Type A is wayyy more common than B or AB, at least in the US (and I think Europe?). Not sure about other regions. That could distort the effect, which looks to be fairly minor in the first place.
> Bombing this meeting in particular seems to be in especially bad taste during a pandemic.
For what it's worth, it likely wasn't targeted. My understanding is that the search space is so short that you can just cycle through it until you find something.