Because Poland has a long and complicated history with the Catholic church. For a lot of people, the Catholic Church represented the only oasis of freedom during the communist rule after WW2 and before 1989, and can be credited with accelerating the end of communism in Poland, especially with a Polish pope being elected merely a decade earlier.

Nowadays though I would call it what it is - it's cancer growing unchecked on the Polish state. And I don't mean the religion - I mean the Catholic Church of Poland is constantly meddling in Politics, influencing new policies, Polish bishops are almost celebrities with a huge amount of wealth, the church does not pay taxes, they are one of the largest land owners in Poland....it's a frightening insitution that only seems to be growing in strength, you'd think young people would turn away from it, but with the current right-wing government literally saying that those who don't defend the church are not real Poles it's quite obvious what the party line is - either you are with the church or you are not welcome.