I think what they mean is that they don't yet have proof it's related, but it's a factor reasonable people could think relevant.

And personally, I'm sure it is. There's no way that that discussions around his resignation didn't involve the pandemic. Even if he had planned 6 months ago to leave now, execs still should have said, "Hey, it looks really bad for you to leave right now, and your people would benefit from stability. Could you stay longer?"