The reason you run into people with ridiculous psn names is because of the number of people who run RTG accounts along with their main, most streamers have multiple accounts for such things so it's likely the people that follow them do aswell. Personally I'm happy just playing with one account, but some people run 2 or 3 accounts.
On another note my best result in recent years is Div1, but I'm stuck in the middle of div 5 right now and don't know why. It might be because I'm not running the ultra sweaty formations with the ultra sweaty players. I'm just chilling this year though, and I've already taken a month and a half off. I only came back a few days ago, but I breezed through the lower divisions to get to my current one.
I don't know if other people are like me and possibly took time to play other games and came back or not, but I would suspect that and RTG accounts are why you run into so many sweats all the time these days. There is also the possibility that the seasonal rests have dropped some people back down a couple of divs. That's the reason why when I first came back on I was div 8, this season it didn't reset me and I think that just because I had only barely hit div 5 before the reset.