I think there's two talking points here.
I think it's an extremely questionable decision at board level given their inexperience of directing a football club. They haven't given Tuchel enough rope to hang himself where by the support from the fan base supplements their decision. If the next appointment goes wrong they have got off on the back foot by sacking a manager the majority of their fan base didn't want to be sacked.
I also think Tuchel has been overrated. You'll hear the likes of Carragher talk about the best managers in the world being in the Premier League and lump Tuchel's name in with Klopp and Guardiola when in reality there are obvious levels. Tuchel has never demonstrated that he can lead this team to any serious sustained success. Yes, he won the Champions League and I'm loathe to suggest it doesn't mean anything as it's a cup competition but it is just that, a knockout cup competition. The league has to be where it's demonstrated that progress is being made and he just hasn't demonstrated that. He also seems to have lost his head a bit in the past 6 months.
People will read this and say the two points may be a bit contradictory, are the owners right or are they wrong, make up your mind, I understand that. I just feel the board could be putting themselves in a situation they didn't need to, this quick into a tenure whilst at the same time I also believe that Tuchel isn't all he's cracked up to be.