>...if they indeed are running a ponzi it would be surprising it could last so long.

There's a practice in the loan industry called "pretend and extend," which basically means endlessly extending credit to lendees who are behind to avoid acknowledging the loss. Remember, in Carvana's case the loan buyer only exists to take on debt, not be a going concern. I think much of the market actually realizes Carvana is a scam, they just see that it is a relatively sustainable one as long as the government doesn't step in. And they don't see that happening, particularly with the current administration.

Madoff’s scheme ran for nearly 15 years, starting in earnest possibly 20 years before that.

I think “long” is very relative to the scam.

Carvana has been written about in the WSJ in glowing articles, that now have shifted to a questioning tone. This may be that inflection point.