This has been done to death, but some people do also forget quickly the context behind 3rd and 2nd finishes and cite only the final position, so the impression is created that we had 2 comfortable top-4 finishes in a row, which we did not:
1. In 2019/2020 we were out of top-4 for 90% of the time and were often literally midtable before Bruno. We only scrambled to 3rd place in the last matches due to Leicester collapse - and were tied on points with Chelsea who were 4th. We finished on 66 points, which rarely is enough for top-4: over the last 10 seasons it was barely enough only in 2015/2016 where City overtook us for top-4 on GD with both of us finishing at 66 points. Expected points showed that we underperformed a bit (had 71 expected points), but Chelsea underperformed them more, so we were 4th in expected points table.
2. 2020/2021 looked more like a comfortable top-4 finish, but again - as posters above detailed, it was also papering over cracks. Even the improved point tally (74) would on average over last 10 season make you 4th, plus actually we had only 66 expected points (and 4th on expected position) - suggesting that we might have indeed been lucky and declined rather than improved from the 19/20 season with its expected points of 71.
So basically under Ole we performed barely good enough for top-4 with no real progress from first season to second if one looks at least a bit beyond headline league finishes and points. And that was with an improving squad. It is no coincidence that the thread "we are a poorly coached team" was created long ago. And I follow quite a lot of football data/analytics/tactics podcasts -I do not consider myself very knowledgeable in this topics - but I was struck how the opinions in them contrasted with the mood here in the summer. The vast majority (especially those who are not United fans) thought that Ole was far from being good enough at this level, found our persistence with him baffling, thought that we are still chasing big names without a proper transfer strategy, squad balance or idea how to fit them and play a defined style of football - and as a result expected us to be a distant 4th at best.
The magnitude of the crash this season was impossible to predict, as it is a confluence of several factors and a chain reaction basically - (1) expectations increased due to 2nd place and a strong on paper transfer window, (2) Ole did not prepare/did not know how to integrate the new signings (3) results caught up with our performances (4) Ole panicked and started frantically changing the approach to games, (5) players were not prepared for it, and became unhappy and confused and lost belief in his managerial abilities.