Funnily enough, Icardi and Keita Balde were quite close since they were acquainted from Barcelona youth sector (not sure if they interacted back then, but it was a common ground for both)
There's another story that never came out, which was that Nainggolan and Icardi threw punches at each other. Either on the bus or the locker room just before boarding the bus.
Two weeks later they cozied up to each other and became buddies

Probably because Marotta put them on detention or something. Plus we had 3 factions in the locker room.
Then there's an incident with Miranda that never came to light, so not sure who fought with whom. But the bad apples were considered to be Icardi, Nainggolan, Miranda and Perisic. They were all shipped the following summer, although Perisic for non-disciplinary reasons (which were about to be, since he got pissed at Conte

). And Perisic would have been shipped in January - and most of the circus could have been avoided - but Arsenal's offer was terrible.
The factions were the ex-Yugoslavs, the Latins and the mostly Italians who were rather neutral. The rather neutral ones also played along with at least one of the other group in case they weren't Italian (like Handanovic).