Two months before the season ended, not seven. After your coach ditched you, not after you sacked him.
And the transition to the new manager happened in summer, yes.
Just pointing out Nagelsmann was employed, it was mid-season when we signed him, and the pace with which the appointment happened after Flick announced he's quitting qualifies for the term "swoop in" - which was the scenario the poster you quoted employed.
But yes, doing managerial transitions in summers is, barring a proper downward spiral of performances, probably the best way to go about. Still, the club should lay the ground work, even the contract, for the new appointment, if they want to move on.
In general, this shows why I think it's foolish to go into a new season with a manger that's already on probation or on dubious grounds, like Arsenal did with Arteta. Bayern should have released Kovac in summer 2019 too, that we ended winning the treble after having to sack the manager early and interim-appointing hiss assistant is just the exception proving the rule.