The only thing that would get the Glazers to leave is the fan resentment. If Old Trafford was empty it would ruin sponsors, merchandise, endorsements etc. But it takes an extreme to reach such a level and there's too much sentiment in fans and emotions that override which is rational as it's natural as many enjoy and follow the sport.
Another reality is if United have a good summer and a decent season the ardent noises about the Glazers goes from many to a few. There's not enough consistent movement in mass level protests / actions.