They probably teased you because they thought he had a crush on you.
Given that his behavior was, admittedly, a little pathetic, you vehemently denied having any romantic feelings for him, and buttressed your position by claiming that you were “just friends.” Besides, he totally wasn’t your type.
Small wonder most Nice Guys choose to run away and complain about it on their social networks instead.
He probably cleaned up his look, started making some money, and generally acted like more of an asshole than he ever wanted to be.
Fact is, now, he’s probably getting laid, and in a way, your ultimate rejection of him is to thank for that.
He probably came to realize, one day, that women aren’t really attracted to guys who hold doors open; or make dinners just because; or buy you a Christmas gift that you mentioned, in passing, that you really wanted five months ago; or listen when you’re upset; or hold you when you cry.
He came to realize that, if he wanted a woman like you, he’d have to act more like the boyfriend that you had.
And I’m sorry that it took the complete absence of “nice guys” in your life for you to realize that you missed them and wanted them.