Can someone explain to me why grown men cry over sports teams?

i am genuinely confused about guys who pour their soul and heart into sport teams and follow every game. maybe its because i grew up in a household where sports was never a big thing for us, no male siblings, and with almost every boyfriend i have had since i was a teenager i never completely understood the whole hype about it.

around this time last year me and my boyfriend had an anniversary dinner planed weeks in advance an he cancelled last minute because of the Pacers - Thunder game 7. i didnt even know what that meant at first. he was basically in tears on the phone explaining how this was the biggest game in OKC history and how he had been waiting for this his whole life.

i watched a grown man cry over basketball and i genuinely did not know how to react.
he called me after they won and was so happy, like genuinely the happiest i have ever heard him. and i just sat there thinking... should i be happy for him? should i be mad? i dont even know what i feel.

i dont think he is a bad person. i just genuinely cannot wrap my head around caring that much about something you have zero control over. can someone explain this to me like i am five?