^ Correct, Mikami had wanted to leave Tango for years now but didn't because he believed Tango wouldn't be safe without him, which makes some sense, Bethesda only acquired Tango for Mikami then told him they want horror games from him, once the Xbox acquisition happened he felt comfortable in leaving Tango and so he did so.
Non-compete clauses DO prevent people from working with 3rd party studios, Kamiya has a one year non-compete clause and he worked at Platinum, a 3rd party company, non-compete clauses are common in Japan. More to that point, Microsoft doesn't even do non-compete clauses anymore, Mikami's contract is with Zenimax, not Xbox or Microsoft. Zenimax still does non-compete clearly, Microsoft does not so it suggests nothing.
Mikami did what he set out to do with Tango, which is to create a studio where he could nurture talent and help create the next great director, Tango's entire purpose under Mikami was that, to find and grow new talent, he has done that with John Johanas and Kenji Kimura. For Mikami to then say "right, now you're all working under me!" completely defeats the purpose of why he set up Tango in the first place.
Y'all are reading too much into things, it actually makes more sense to think about the reason he set up Tango (to nurture new talent, allow them to create their own games) and consider why he then wouldn't want to say to all these new leaders "right, I want to make my dream game now, so you're all working under MY direction now" His goal with Tango is achieved, he did what he set out to do, now he's moving on.
Could Microsoft have set up a new studio entirely for Mikami? Possibly, maybe they should have done that, but I don't see him leaving Tango as a sign of a relationship breakdown and more because his goal of Tango was complete and now he is moving on. Mikami has even spoken multiple times in the past of wanting to do one more game before retiring.
There's multiple possibilities of where he goes now, he could join M-Two where his old buddies are, he could join Capcom where his old buddies are, he could join with Kamiya, his old buddy, all for one last hurrah with his old pals before setting off into the sunset. He always has said he only has one big game left in him.
Tango isn't clueless without Mikami, he created a brilliant team and that team released the highest rated title that Tango has ever done, without Mikami's creative direction at all, they'll be fine to operate without him, they'll be fine recruiting without him, he has succeeded in his mission, Tango was never all about Mikami in Mikami's mind, only Zenimax's (which he didn't like).