I think you have to know the history of Jews in Europe to understand just why they are disproportionately represented in intellectualism. You also have to know something about Judaism.
Theologically, Judaism believes God to be in the details. The more you learn, the more you come to understand God. I tend to think Christianity and Islam tend to not want to question the nature of God so much as Judaism does. When you excel in knowledge, God becomes closer as you're examining the nature of God no matter what the intellectual pursuit. Judaism has an intense emphasis on knowing Talmud and Torah. Talmud is derived from Torah; it's a running commentary by Torah scholars. Imagine there not only to be the Bible, but an accompanying annotated text of notes from the great Biblical scholars sharing their insights. Just by that tradition alone, there's a sense that each person can approach and understand God best through study and debate. It's a very personal approach compared to Christianity where most sects believe intercession between church and God is necessary. Priests and ministers must be intermediaries. Judaism has nothing like that. Rabbis aren't required to act as intermediaries and the opinion of any rabbi is open to question and debate.
Though it's overhyped of late, true scholars of Kabbalah take this most to heart. They pour over, have even memorized Talmud and Torah, to discover new clues to the nature of God. If Christians place God on a throne way up in the sky requiring a telescope to be seen, the Jews have God under a microscope.
This theological difference, I think, helps increase the sense among many Jews that learning is the most noble of pursuits. If you're going to learn something, learn it inside-out because unless you do, then you're not really living life. To know something means to investigate, research, gather opinions, then draw a conclusion. Certainly that's true for any learned person, but for Jews it's almost second nature because such study is so emphasized on a religious level.
The other factor, history, makes a great deal of sense. Jewish persecution is no myth and it has gone on since the days of Egypt, but where we see European Jews really excel since the fall of Rome, is in finance. Once Rome became Christian and, following that, the collapse of Roman civilization, Jews had one role that could not be occupied by gentiles and that's as a financier. Christianity, from the beginning, had prohibitions against usury. Now we consider usury to be the charging of exhorbitant interest rates, but back then it meant charging any interest at all. To be loaned money was impossible as nobody could loan it to you unless they did so as a favor. As you can imagine, that did nothing for the banking business. The Jews however, had no such prohibitions. Throughout Europe Jews were grudgingly tolerated by various rulers because only the Jews could loan money when, let's say, taxes weren't quite so forthcoming or the Prince of Whereeverandall was a little too frivolous on his coronation. You needed money, you went to the Jews. If the Jews in a place were lucky, then the Prince paid them back with interest. If they were not so lucky then the Prince would sponsor some progrom and kill or kick them out of the realm to avoid paying them back. Consider for a moment though, all things that charging interest applies. It's the foundation of banking, entreupreneurship, and modern commerce. All these areas were confined by Christian law, to the Jews.
Now if you were a money changer, desperately needed in medieval Europe when every tinpot dukedom and marquesate had their own currency, or a money lender or a financier, you had to learn how to manage accounting books, the principles of commerce, mathematics, the economic quality of goods and services, and cagey enough not to charge so much as to get your little ghetto exiled or worse. This required an extraordinary amount of learning quite foreign in countries where 95% of the population was illiterate. The life of a European Jew was precarious and uncertain. Wealth had to be portable and tradable, hence the (not unfair) hoarding of gold, silver, and jewels by Jews. Owning land, the measure of wealth until the industrial revolution, was pointless because at any point you could be driven out of town in the great majority of places you lived or the land could be confiscated. It was much safer to bury boxes of precious metals or sew jewels into clothing or placed under false floors in oxcarts. Those were valuable things you could trade anywhere at any time.
Naturally, not all Jews in a community were involved in finance, but many were. Others became merchants, knowing that to sell their goods to anyone other than other Jews, they had to offer good prices and superior quality. Merchandise was fungible, could be transported and traded. There was little use to being a tradesman as no one would hire you save other Jews. That's not to say they didn't exist. Jewish communities lived in ghettos which were essentially microcosms of the larger community around them and so some tradespeople were necessary, but they weren't the focus of commerce.
This is in stark contrast to the rest of medieval Europe when the great majority of people were vassals in a manor. You apprenticed, journeyed, and then became a master craftsman. Either you labored or you made stuff. That was all you did. Only your lords and ladies had the education (sometimes little of that) to manage everything. Education served no great purpose for most people because it didn't enhance their income. If you were a beet grower or a baker then that's what you did. Social mobility was extremely difficult to come by even in small increments.
Jews had no such problem. They would always be at the bottom of the gentile social world and so had no problem working at all levels of the system because they were outside the system. Jews had access to everyone from the lowliest tanner (and tanners were as low as you could get) to the king himself to the abbots and priests to bishops and cardinals... even the pope.
When I add this all up, I can't help but see how Jews have excelled in the arts and sciences. There's a tremendous tradition of learning, of business, of having to be prepared, of having to work harder than others to achieve, and of desiring to learn everything they can about a subject so as not to be caught unawares. Adversity makes people tough, practical, and pragmatic and I don't think any group short of maybe the gypsies (who the Germans imprisoned and exterminated too) has suffered so much in Europe.
