First of all, I can prove you wrong because you used the word “all”. You have left no room for any exception and you can’t possibly mean that each and every European basketball player intentionally acts and flops. Second, I don’t think that just because a basketball player flops, it means he is soft.
I think it is more likely he is trying to get the referees attention so that a foul can be called, and he can then have a chance to score more points to help his team win the game. He may also be having a hard time defending an offensive player and so he chooses to flop in order to stop his opponent from scoring.