Tuchel's problem is simply that his entire career is a lie.
In his previous clubs, he appeared to be a good tactician, but he had two important factors on his side that made him look way better than he actually is:
Field generals on the pitch: At Dortmund, he had Hummels and Gündogan. In PSG, he was lucky to have Verratti, Neymar and Thiago Silva. Same with Chelsea, where he benefitted from Silva (again), Azpilicueta, Jorginho AND Kanté. Some of them were amazing passers/creators and some were great defensively, but they all shared an extremely high level of football IQ and leadership qualities. They could coach their teammates without requiring Tuchel to micromanage them or come up with highly sophisticated tactics. At Bayern, Müller and de Ligt are the closest thing to field generals, but the former is too old and slow while not being "silky" enough as far as Tuchel is concerned, while de Ligt is also "too slow" and pretty injury prone.
Benjamin Weber: Believe it or not, this guy was the real brains behind Tuchel, even more so than his field generals. Just think about Tuchel's apparent greatest strengths: he was very flexible and reacted pretty quickly to what was happening on the pitch; moreover, his game plans/preparations in big games were usually extremely successful. Statisticians and video analysts have something to do with them, don't they? Fittingly enough, Benjamin Weber was his video analyst starting from his Mainz career all the way until he got sacked by Chelsea.
He coasted on these guys' talent and hard work throughout his entire career, shamelessly stealing credit from them like Gilderoy Lockhart from Harry Potter. And since he's a charismatic extrovert with a silver tongue, he knew how to compile their ideas into cool soundbytes to parrot the content to sound like a dashing genius instead of the utter fraud he is. That's why he still enjoys the reputation of being a highly intelligent and competent coach in footballing circles.
Being a man of limited ability and intelligence, he doesn't like it when he's called out on his BS either. Back in Dortmund, he ran the highly data-driven scout Sven Mislintat out of town because he found his scouting methods too technocratic. Mislintat made heavy use of stats and data when scouting players while Tuchel was in favor of divining their attitude from their video footages. Guess whose methods are better? Mislintat's work at Stuttgart, a club infamous for being a hopeless case, is finally getting results, with talented players bought for reasonable prices being coached by a talented manager. On the other hand, Tuchel almost always wants one-dimensional physical beasts, pace/flair merchants or mediocre old players just because they're "experienced".
At Bayern, he has Müller and de Ligt, but he prefers physically more gifted players than them, and doesn't appreciate their intelligence and opinionated personalities. That's why he always loses the respect of his players soon, because he's highly dependent on field generals to succeed, but it's only a matter of time before he's called out on his incompetence and stupidity by them.
Not only that, but he's also morally bankrupt. Back in Dortmund, he actually did want to play the Monaco tie right after the bus attack, but he then turned out and claimed he didn't but Watzke forced his hand to play the tie to save his own ass and paint Watzke as a monster at the same time. He even said "Am I supposed to beat Bayern with these wimps?" all the while being the biggest wimp of all by throwing others under the bus for his own misdeeds. Sure, Pit Gottschalk isn't known as a pillar of accurate reporting, but why would someone risk going to court and have his reputation utterly ruined by lying?
Not to mention he believes in ayurveda. Far be it from me to judge the personal spiritual beliefs of others, but ayurveda isn't just spirituality, it's a medical doctrine. It's nothing short of screwed up that someone responsible for the health, safety and performance of give-or-take 20 players actually believes in unscientific quack medicine that he probably doesn't bat an eye on having used on his players. If there's any sense left in society, such a person forfeits the right to practice his job and has his coaching license torn apart.
He embodies the currently popular fake-it-till-you-make-it culture, just like Elizabeth Holmes and Sam Bankman-Fried.
