Abhimanyu being called Krishna's son doesn't mean Krishna was his biological father, he is called son of Arjuna and Subhadra more times and his birth is described in detail
In my opinion it has more to do with the alliance with Virat, Arjuna had nothing at that time, Krishna would have taken guarantee of Abhimanyu, Why would Virat marry his daughter to people who have nothing?
Look who we have here. Hi nora