There are more explanations.
Karneval/Fasching/Fasnacht celebrations are hugely popular in the South and West and virtually inexistent in the North and East.
The east is generally poorer (so easterners travel less) and has less popular tourist destinations - except Berlin, which has been hit badly enough.
Not a tautology but yes, that is essentially what I am saying.
I just found it weird that people seem to be focusing on all sorts of factors like family structure, median income, winter holidays, Fasching/Karneval celebrations etc (which of course also play a role) while completely ignoring that higher population density facilitates the spread of a novel virus.
