Buttigieg is far and away the best candidate the democrats have. If democrats had the courage of their convictions he would be their choice, but they are cowards. It is democrats who are not ready for a gay president, hard line republicans won't vote for a democrat regardless of sexual orientation.
Any hesitancy could well be the concern whether fellow Democrats are ready in sufficient number for a gay president. So I'm guessing that there may be some second-guessing going on here. Also, don't discount that some Democrats are left of him, so whatever hesitancy there may still be may not be limited to orientation. In any event, Buttigieg is a new face on the national scene. He is a contender. And the clock is still running.