I wish I could upvote your first paragraph and downvote your second -- the latter is a fully general counterargument against the possibility of delusional bubbles, since, in most such cases, the people bidding up the bubble asset do have skin in the game.

Well, of course you're correct. But the market is usually rational, and to the extent that it is not so, it generally corrects itself relatively quickly. Now, it is possible that this is one of those cases where that isn't happening, but we should require fairly strong evidence to believe that. That evidence has not been provided in this case.