First of all, he was holding back at the beginning of his career and wasn't very "controversial". Second of all, it's pretty normal not to be famous when you're low in rankings or not ranked at all. But the point is, once you get famous and people recognise you - you can't just switch it off.
It's not like everyone will get a sudden amnesia and not know who Sean Strickland is just because he no longer holds the belt.
I used to know Strickland only as a top 10 Middleweight fighter. I honestly think there is nothing special about this guy.
Hanadawa said it perfectly, few people knew who Strickland is before he entered top10. For me he was also just an average guy, who sometimes get microphone during conferences and say weird stuff. I think he has started gaining attention, when he made fun of Adesanya on UFC 276 and got KOed by Pereira. But he might get that UFC curse, when you star lights bright, and then dimes quickly. Not like people will get amnesia, but they will turn their focus on other guys that are about to have a title fight. There are a lot of guys who were champs, but not look like a card fillers.