I mean, crushes that you saw all the time and you were close with, and ones that weren’t good people. My ex-crush, this Polish girl I nickname “Helen” on here, turned out to be a Christian with internalized homophobia and was an ableist asshole who hated special education students and made fun of me behind my back.
As others have said, time. Also, the realization and repeated internal reminders to yourself that they were not who you thought they were.
It’s very easy to build up someone in your head to be better than they are and to fill in the gaps with positive assumptions, especially when you’re crushing on them. You have to realize that those fuzzy feelings were in your head. The feelings weren’t based off reality, and they obviously weren’t the same feelings in that person’s head. At the very least, those feelings weren’t based off the full person, because you didn’t know them fully.
The version of them you liked didn’t exist, because that version wouldn’t be (in this specific case) homophobic, ableist, hating special needs students, and making fun of you behind your back.
Yes, it may hurt to remind yourself of the reasoms they are shit, but it’ll hurt less than allowing yourself to pine for a “what could have been” that was based off a version of them that only existed in your head.