Well you cannot go by force and make rash decisions. He had probobly some options but not good enough for him,he also asks for a big salary and some additional things that other clubs cannot get for him. He will need to be satisfied with europa league this season and try with Man utd to get the champions league spot for next season
Yes, I think it would not be wrong for Ronaldo to stay at Manchester United and try to bring the team to get more wins and qualify for the Champions League next season.
Because if next season Ronaldo is still at Manchester United, then he can also enjoy the Champions League again even with the same team as this season.
Now is the time to focus on Manchester United and win more games in the Europa League first.