Why do guys take off their shirt in front of you?

A guy I’m almost certain have a crush on me took of his T-shirt in front of me at the gym (yes I go to the gym sometimes we barley have any cases in my country). He has started doing that, he flex his biceps in the mirror in front of me and takes off his tshirt like yesterday he didn’t have a T-shirt on as he was flexing in front of me then he walks around with his chest extremely puffed lol. He has a lot of muscles but still, why do guys do that?
Why do guys take off their shirt in front of you?
Post Opinion