As noted before, Brock Lesnar is done with WWE for the time being with his contract expiring in a few days and WWE writing him out of storylines when Kurt Angle refused to grant him a rematch for the Universal title.
The reason he was pulled off of Raw – even though he was previously advertised as being there – is because no one on the creative team could think of an idea for him that would make sense. One idea was for Braun Strowman to beat him in a match but Lesnar only had the one appearance left on his contract and technically no matches left to fulfil. The other idea was that he would go crazy and get suspended but that didn’t seem to serve WWE any good purpose if he was leaving anyway.
Source: Wrestling Observer Newsletter. Subscription information & prices available at f4wonline.com