I’m sure he was let go with a promise that he’ll be back on board after the victory—when conservatives are no longer wanted or needed. That’s how Romney works.
He was not “let go”. He quit and made a fuss. I bet the Romney campaign did everything it could think of to keep him.
I'm afraid you're right.
One important qualification: the secular part of the conservative movement has numerous homosexuals in prominent staff-level positions, though not usually in elected office. This is an “open secret” in Washington and numerous state legislatures, and there are probably a lot more people “in the closet” who are known only to a very small circle.
This problem isn't limited to Romney by any stretch of the imagination, and involves people who have much better conservative credentials than him.