Honestly, I've never really liked Diego (always thought he was a bit of a tool), and watching this whole thing with Fabia was pretty hilarious at first. But the more I think about it, the more horrible it seems.
Diego is almost certainly suffering from CTE, and now he's got some complete clown with no training and no clue about fighting filling his head with nonsense and training him instead of a proper team.
The guy is clearly taking advantage of Diego's mental short-comings. Fabia knows exactly what game he's playing. The guy is an absolute scumbag. When Diego falls apart--and there's no way he won't with this guy in his ear--Fabia is just going to ghost him and latch onto the next gullible, punch-drunk, low-intellect mark he can find. This farce of his should be considered criminal. Watching him getting away with it is pretty fucking gross.