We simply have no idea, and from some reactions of other riders it almost looks like they don't either.
Okay, they probably know a bit more than we do, because we are absolutely clueless, aren't we?
To me it looks like some kind of blood-doping, some pretty old-school thing just modernised. Not that I know anything about these things, that's just what it resembles, especially since Pogacar doesn't have the most constant highest level, very high, yes, but it looks like he can up his game for certain events/ days. This also doesn't look like some kind of elaborate know-how about the best mix of hormonal micro-doping, the way that a year ago I thought doping today was done.
My best bet, and it's really nothing more than a bet, is that they are willing to take bigger risks, go for full juice instead of holding back, not working on the safe side, but risking to get caught, gambling on not getting caught.
He's probably going to win his second Tour this year, so of course the focus is all on him, but it's not like he's the only one who showed ridiculous stuff this year. Padun and Cavendish are up there as well for me, on a lower level a few others as well.
He's probably pretty talented to begin with and also a good responder.