[dogscoff]

I know the exact location of all ships which could fight against player A1.

You misunderstand me. I suggested that the fleet could have been in a battle with itself as a result of the crew insurrection intel project:

Player b2 uses crew insurrection to steal 2 or 3 of the more powerful ships in a1's mystery fleet. Battle begins, and because the insurrected ships are armed with allegiance subverters, they capture even more of a1's ships, which capture more ships... this kind of thing can and does happen.

Soon b2 has almost as many ships in the sector as a1, and they have all used their allegiance subverters, so they resort to regular weapons and blow the crap out of one another, leaving only a handful of ships alive.

While a random event is technically possible, I can't think of any that would destroy nearly 200 ships at once - one or two ships yes, 200 no.