I don't recall what exactly happened between them, but Kanye really wanted to come for Jimmy Kimmel in the past. It was either a monologue joke, or the breakup with Sarah Silverman. Knowing Jimmy Kimmel, he probably didn't even care. He just laughed it off. That's more press for him, after all. Kanye is slaying with this diss. It feels so petty because there's no way that Jimmy Kimmel deserved this, and because it simultaneously makes fun of Jimmy Kimmel and boosts up Kanye at the same time. If you can diss someone while at the same time telling everyone that you get good pussy, you've just achieved a God-level diss.
The caps might lead you to believe that Kanye is made, but remember, he's just lazy. Hey might have even wrote this tweet while in London. All signs point to yes.