I checked out the link. Didn't the parent comment say that it was Putin — italicized — who threatened to nuke Ukraine? Wouldn't the evidence for that need to point at specific Putin's words to that effect?
What makes you think that Kadyrov is Putin's likely successor? Anything could happen, of course; but as a Chechen and a demonstratively, fervently devout Muslim, Kadyrov would be an even scarier figure for the outwardly Orthodox Russians than Stalin was.