I don't know if Brock doesn't have any interest in picking up his old wrestling style, or he wants to play up his UFC style. Makes for some awkward matches.
All brock is doing is securing himself 5 million dollars. Helps pad his bank account, pay his medical bills, pay for his kids' upbringings, buy a couple acres of land in the countryside...
he's a pretty low-key guy IIRC with a love for the outdoors, so a ranch next to a lake and some hunting grounds is probably what he's going for, and that'll cost a few million.
He absolutely hated the grind of the WWE schedule, so if he can make 5 million dollars for a few casual appearances and a handful of PPV matches, great.
He does seem to be having slight trouble adjusting back to "pro wrestling," but when you're working as infrequently as him and you have no plans to stick around, what's the point?
Easier on the body for him to go with the brawler style of wrestling (And matches with his UFC experience) than the grappler from his earlier stint, anyways. He's got enough health problems at it is.