So there isn't really a whole lot to say about this because if you even looked away from the screen during the start of the match you would have missed it. The fight was over in 5 seconds.
Jorge Masvidal delivered Ben Askren his first defeat ever, in a truly embarrassing fashion. As the picture indicates, this happened as the result of a flying knee that actually resulted in Masvidal hitting the canvas pretty hard afterwards. Askren was a ragdoll on the mat after the contact.
Masvidal then struck Askren two more times after the initial strike and many people think this was unnecessary (it was) but being so ramped-up about a fight and the fact that you need to finish a fight and only stop when the ref tells you to. Jorge at no point ignored the referee's instructions so there is no foul here. The fight was actually over in 2 seconds, but the ref did the right thing by waiting to see if Askren was still conscious and capable of continuing, which he clearly was not.
In the post-fight interview Jorge said that Ben was "a bum" and that he had been talking S**T for a long time about this fight... which really isn't very uncommon. Personally I felt a little bit bad for Askren because I know from being briefly involved in fighting sports how much time and dedication goes into this sport even at a very low level. I would imagine that Ben trained intensely for years leading to the moment, only to have the lights switched off the very first time he was hit.
However, the KO is as much his doing as it was Jorge's. One of the worst things you can do in a fight is to actually LEAN IN to an oncoming strike, especially a leg or knee... and that is precisely what he did. Personally, I hope that a rematch happens if Ben can recover from this very embarrassing defeat... he is truly eating "humble pie" right now.