> What made the Ukrainians think he was available for such an offer? <
The Ukrainians knew from the get-go that Vindman would not be able to take the offer. I think it was an attempt to flatter and manipulate him. Geez Vindy, you’re such a great guy. Please consider being our defense minister. Because you’re such a great guy.
By the way, there’s a few little things we need your help on.
(And it says something about Vindman that the Ukrainians would even make such an offer.)
Or it could have been a joke? Or he made it up to burnish his reputation.