Him not being the main man wasn't a consideration last time. And I agree with you. I think it was monumentally stupid. Paying him £250k a week backs Man U into a really tight corner when it comes to sell-on. Who else could pay him that? PSG? Chelsea? Maybe Real Madrid. City?
Unless he gets a similarly extortionate contract somewhere else, Man U will still be paying a proportion of his ridiculous wages for another 2 seasons. Last time around, he would have been much easier to sell and make a profit on. If he goes to Bayern, he won't be getting anywhere near 250k per week.