I won't accept anything like a mistake winning or luck here, Bayern Munich might not be in their utmost feat but they deserve what they got, after all, they didn't get to the first 2 levels by chance before they eventually win the league among the 18 clubs who contested it. Bayern Munich is a strong name in Bundesliga and might retain this for a longer time, and even now, they are facing challenges, if not, the point they were supposed to gap their next opponent should be much. This is the same thing that cost them the Champions League, but let's be patient for Tuchel, though his first impressions are not good, I still believe in the club.
Besides, we should not be using the financial stand of a club to be judging all the time, maybe we can learn from Seria A this season, it's more about the coach and the team thereof. Once they are good and determined to play, then they can be so surprising.
Isn't it a bit too romantic to say it is more about the coach? I think it is a mixture of many things and the coach plays a big role. I doubt that Guardiola would have won the Premier League with Southampton or that Tuchel would win the Bundesliga with Augsburg. Money is a big factor 90% of the time domestically and from time to time you have some deviations where a club actually becomes a statistical outlier and wins something despite weaker financial resources. But generally speaking, money is important. Cut Bayern Munich's money in half and see how many of their players can be retained and then see whether they are going to win the Bundesliga.
I am only talking about the domestic competition here. Internationally we have seen that a club like PSG fails all the time, but domestically PSG is literally buying the Ligue 1 title. When Dortmund had Lewandowksi and was extremely successful, it was only a question of time until Bayern bought him. Players follow the money.
It is not necessary to seek out exceptions now as I am fully aware of that, but correlation between money and a team's success domestically is especially positive when the snowball already began to roll. It's not the same when you try to invest half a billion like Chelsea and hope you can beat Manchester City that season because they didn't invest that much. However, looking at spending over the course of a decade, you won't be surprised that Manchester City is leading the ranking alongside PSG with around a billion of investment. But in this case Manchester City has had a world class coach for a long time now and PSG didn't.