If they were discussing nuclear war and Trump said “IF you do it, I’ll hit Moscow” didn’t that make perfect sense?
If they were discussing Putin wanting to take Ukraine or Eastern Europe, it makes perfect sense as well, and more sense in the context. Putin already knows if he launched a nuclear strike that our response would doubtless be likewise. What he didn’t know, and would be interested in inquiring about, would be an individual President’s reaction to a nonnuclear invasion of a particular sovereign European nation. He would want to see first hand Trump’s reaction to the question and if that reaction had actual resolve behind it. Putin behaved, during Trump’s administration, as if he genuinely believed Trump had told him to take Ukraine would result in a nuclear strike. Putin behaves now as if he had asked the same of Biden and had instead been told, “No, I would not go that far to defend Ukraine,” or had been told there would be retaliation unconvincingly.