He kept trying to impress and compliment her and just ended up insulting her or putting his foot in him mouth. For instance, he tried defending her from Dave’s teasing once really seriously, without realizing Dave and her were really close friends and that the teasing was playful.
For a long time he thought that girls only liked really tough and macho guys (mostly because that’s what his dad told him, and it seemed evidenced by his older brother Summoner, and also by Vriska always telling him he needed to be tougher).
EDIT: Vriska saw it going on and made fun of Tav for his crush, while secretly being pretty jealous. :p
At their highschool graduation he blows a gasket, gets in a fight with Sollux and Feferi, storms onto stage to ruin Kanaya’s Valedictorian speech, and generally makes an ass of himself. None of his friends talk to him after that.
Cheloneuniverse 