Vince McMahon wants to sign Brock Lesnar to a contract extension when his current deal is up, which may explain why it was so easy for Lesnar to get a one-off return to the UFC. The WWE considers Lesnar to be a model employee, as he always does what is asked of him. His desire to return to the UFC hasn't changed the minds of Vince and other officials.
On related note, there's been talk of Paul Heyman returning to TV before Lesnar returns to build his SummerSlam match. There's been talk of introducing new "Paul Heyman Guys" as part of the brand extension.