1) God arose as the most logical explanation for things otherwise unexplainable by people. If there always was a god, then for the first few billion years, this planet did not have beings capable of acknowledging its existence. If despite this, there always was and is a god, and if the "end of days" is truly at hand, then life on this planet was more than 99% wasted by being filled with things that weren't able to comprehend a god.
2) As our knowledge has grown and compounded upon itself, we are becoming ever less in need of a god to explain things. Complexity has resulted from small accumulations of changes to simplicity. If life needs a creator to explain its complexity, then that creator must by definition be even more complex, thus requiring an even more complex creator, ad infinitum.
3) Because humans are (presumably) unique on this planet in being aware of our own mortality, the promise of a continuing life after death is a great selling point for acquiring members to "clubs with rules" (aka religions). It's hard to trump someone who can convince you that while you're poor and miserable now, keeping "in line" with the rules will grant you rewards after your death. It's also a great way to maintain class divisions.
4) The strictly fundamentally religious often eschew information or lifestyles born of science which contradict religious teachings. In the USA, there have been attacks on teaching evolution in public schools. Be very wary of any mindset that praises ignorance -- knowledge is a light in the dark. The battle between Socialism and Capitalism was based largely on the premise in Socialism that for it to truly work, there must be no Capitalism anywhere else, i.e. no alternative.