Caruana allowed Karjakin to play a strong exchange sacrifice. Ironically sacrificing an exchange is a very common method to defeat weaker players who aren’t weak enough to blunder material. If you wonder where Karjakin’s million dollar match preparation against Carlsen went, I guess you can see an example here.
After this masterpiece there is a very good chance for Karjakin-Carlsen Reloaded. I don’t see Wesley losing with white to Karjakin and I don’t see Karjakin beating Ding. Caruana needs get lucky with black against the high variance player Grischuk. It would be a catastrophe for russian chess of course. One thing is clear: Karjakin can handle pressure, while I am not so sure with Caruana.