B/c there are currently like NO live sports going on right now. If Dana can show UFC events every weekend......even if they are free, he's going to get people, who normally don't watch the UFC, to tune in. It's a huge opportunity for him to grab some new "fans" and viewers who might become paying customers in the future.
It's like giving away a free 1-2 months of your product hoping people will enjoy it and pay for it later. And, as I mentioned he has ZERO competition right now. Heck, gamblers are betting on simulated games and eSports b/c there is no live gambling and gamblers gotta get their fix too!!
Put it this way.....sit at home and watch Tiger King for the 4th time or tune into some live sports liek the UFC?