#1 The McMahon family won’t let Lesnar do it
Brock Lesnar and Paul Heyman aren’t coming to Raw alone. The McMahons will also be there to punish the duo, as they have insulted WWE.
As of now, it is likely that the WWE will suspend Lesnar for disrespecting the company, because it's a common way they punish wrestlers. Stephanie has already suspended him from WWE for 30 days and it wouldn’t be shocking if it happens again.
And in this time period, he could either stay at home or return before his suspension ends to cash in the briefcase. Vince is great at fooling the fans and he has done it many times.
The Beast has won the briefcase, and there’s a reason for it, which isn't to lose it without winning a title. Whether you like it or not, it’s almost confirmed that Lesnar will successfully cash in his contract. All we have to do is to wait and see when it happens.