Why NT's befriend autistics only to backstab and avoid talking with them

As an autistic kid i had a lot of "friends", ​but after some time when they know me better these people(mostly NT's) block me for nothing on social media, avoiding talking with me or talking sh**ty stuff ​about me behind my back with their "real friends". Remember i befriended metal girl who was empathetic to everyone including me but after some time she stopped saying hello to me, wasn't interested with my topics and just pretended she doesn't know i exist. She said that she stoppes talking with rude people. I wasn't rude, i never said bad stuff to others. And it was peak of iceberg.​It was happening 3-5 times with other people but had worse consequences like bullying​. ​Is there any reason why is this happening?