You are also right that sports is not like something that one person just came here and he just liking it. There can be exceptional but most of the people for liking a sports or a team they have to first gain knowledge and understand the sports then they will choose the favourite team for him on depends on his favourite player or the performance etc.
If anyone notices, after watching our games for years, we select one favorite team and sometimes change them.
When it comes to truly immersing yourself in sports events, studying the methodology and history of how teams or players perform, and building a foundation for a deeper understanding of the game — very few people actually do that, in my opinion. Most just place bets by pointing a finger at the sky; for them, sports betting is hardly any different from casino games.