Well, in the Governator's defense, the HRC and EQCA really, really botched the campaign, and thought it was going to be a cakewalk. They were a little blindsided by the amount of support and money the Mormon church pumped into the Prop 8 campaign, but those on the side of equality spent even more money and just did a shitty job of it. Arnold has always been a supporter of gay rights, and refused to appeal the same-sex marriage ruling and the ruling that over-turned Prop 8, which basically should have killed the issue in the court system except for the far-right groups that got a bunch of high priced lawyers to argue that they could defend Prop 8 even if the government wouldn't.
Kudos to Maryland for getting on the right side of equality and history.