Personally, I think the real deal here for Bayern Munich is the fact that no team in the league is close to then in terms of money. They are the richest in the league and can afford to buy any player in the market which even the second team in the league will struggle to get. In terms of money they are miles ahead of all other teams and this gives them the edge over them.
Just look at the total value of Bayern Munich current squad; no single player can even come close to half its value. This proves their far superior financial strength, they prioritize titles, even after winning the title the previous season, they consistently strengthen their squad in every transfer window.
If Dortmund weren't constantly selling players, perhaps they could be on par with Bayern. This season it's clear that Bayern will once again dominate.