They're apparently getting at least $400 million a year which is a huge jump over the current deal of $250 million so I can see why they made the jump. On top of that, it's apparently going to include everything from Smackdown! to WM to even NXT in the long run, which is going to be interesting considering the separate deals for each of those series currently in play.
WWE/TKO making big moves & breaking tradition in a very risky but lucrative fashion because this is going to force normal diehards to either get Netflix or increase the rate of piracy on the open seas. All these streamers are trying to get a lock on the live market anyway.