Tuchel was successful in the first match. He blew up Dortmund's defense. The players of Bayern Munich played great. At the same time, Bayern Munich managed to occupy the top spot of the table by removing Dortmund
No doubt about ability of Tuchel as he got good management results in Mainz, Dortmund, PSG and Chelsea. Bayern Munich have a good squad and they have winning tradition so it would be more easily for Tuchel to work with them than with PSG. In addition, in Bayern Munich, star players don't have big privileges like PSG gave their star players. It is great success as Bayern Munich already took over the first position from Dortmund and they are on a good track to win Bundesliga.
But Munich's main goal is the Champions League title. And it won't be easy for Munich. In the next match, they will play against the mighty Manchester City. Manchester City is a very strong team. The coach of the team, Guardiola, is very experienced. Also, their main striker Haaland is in great form now. Looking forward to seeing what match tactics Tuchel adopts to stop Haaland. Manchester City's home match against them is very challenging.
Manchester City and Pep Guardiola won't feel comfortable after Bayern Munich got that big win over Dortmund. They got a signal that Bayern Munich are actually strong from their matches with PSG (in round of 16) and with Dortmund days ago. They would feel fearful about history of Tuchel to win Champions League as an alternative coach in middle of season.
I don't subscribe to this as I know you speak as a fan. If a team is to be tagged great, one reason should be how they react to a scenario like this. Pep Guardiola and Manchester City will not be shallow enough to react in this way towards Bayern's victory. This will only give them more reason to triple their preparation and set the system much ready for the clash ahead, seeing that there is an upgrade in the opponent's performance. Guardiola I know will only learn from Dortmund'a weakness, use it as a guide, and also devise different methods of approaching Bayern in a way that will yield him good results.