He could have always renegotiated his contract to a lower one and then he'd become an absolute legend, while being repaied over the years as a club embassador that does nothing
There were definitely alternatives, he chose to make a bank which wouldn't be a problem if he didn't use some social issues for PR earlier
You can be knowledgeable in more than one field
You can, but you need to prove it by showing your know knowledge in said field. In that case, you listen to someone talking about hockey that happens to be a successful footballer, not because he's a successful footballer
I don't know Cech outside of football, but I'm assuming the reason you and others (in particular, hockey people and drummers) listen to him on those topics and found it to make sense. Yes, without him being a successful footballer you'd never heard about him, but he still needed to prove himself on that
Then you also have the obvious that having certain issues in some issues raises your commercial value to a degree that hockey and drumming don't
There you have it, you listen to him on those topics because of that. His famous because of his football merits but his opinions on those topics matter because of what you pointed out