exactly, you don't understand it and that's ok. Many people are very passionate about a lot of things. You are just not passionate about sports (or team sports, whatever). You don't have to be. But football is kind of a big deal being the biggest sport tournament in the entire world by far (or at least western world)
I assume you are from the united states, and I (am from Argentina) work with people from the USA, and I also don't understand many things from your culture, and that's ok too :)