Ten Hag would have been a brilliant hire a few years ago before Ole spent 400m building a new team.
The problem now is that you have the team Ole built and trained, the spine of the team is at their absolute peak ages, but its not clear that the players are suited for Ten Hag's kind of football that requires an emphasis on retaining possession, positional discipline with and without the ball, and high work rate. You have too much prime age talent to embrace a totally new project that will only really really work if you either replace half the team with other players who can play a different style or spend several seasons trying to teach those existing guys to master a completely different kind of football. This is on top of the very real question of whether Ten Hag has the stature to command a dressing room with players like Ronaldo, Pogba, Bruno, and Rashford, especially when some of them might end up marginalized in the new project.
IMO, you need to maximize the next 2-3 years with Maguire, Varane, Bruno, Pogba, Shaw all in their absolute primes and Ronaldo playing out the end of his career. The way to do that is with somebody like Conte who has the stature and personality to deal with anybody, knows how to whip a group of experienced players into shape quickly, and also plays a style that, while very tactically sophisticated, relies much more on moving the ball rapidly vertically than Pep-like possession and positional play.