He quit the game between the first and the second round, and I guess the game isn't rigged to have round transition animations interrupted so his head popped once round 2 started.
If you're asking why his head popped, when your opponent rage-quits in MKX, their head blows up and you get the win.
I'm really liking all of Jax's variations, trying to figure out the command grab's timing is hard as hell but i'm getting there. I don't want to sadden you but Pumped up is kind of my favorite ATM because Super Gotcha is really fun and satisfying to do.
I guess this quitality thing really works, I've only had two people rage quit on me in these four days, where as in MK9 that shit was popping off like every 3 fights.