Hi <3
Thank you for this question! Ajax was teasing but didn't realize that his teasing would have such an impact on Diluc. He and Kaeya made jokes about Diluc being the kind of guy someone would try to get into bed for a bet (because it's a popular movie trope) before and that came out in that moment - ofc Kaeya never meant for him to say that to Diluc's face. Ajax didn't mean to bully Diluc, he just didn't anticipate that his words would be taken so seriously and that Diluc would react so badly. Kaeya did not beat him up, and they're still friends after this. He did probably make him buy him snacks for the next months or so though (but it's fine, Ajax is loaded). Diluc and Ajax never really became friends after this, but Diluc tolerates him since he's Kaeya's friend. Ajax is.. well, he's Ajax about it, so it doesn't faze him when Diluc is a little dismissive towards him. :)