You got assigned as his brand new partner at the BAU, Spencer. You were the best at reading emotions, have a high EQ, and are the best at everything Spencer wasn't. You were also smart enough to keep up with him intellectually. He was struggling and pushed himself to keep up with you. That led to him being extremely frustrated with you but also intrigued by you. To Spencer, It's like you spoke a language he couldn't read, but you read him like a book.