Lesnar's a mercenary, Rollins and Kane work on behalf of the Authority, if Lesnar goes against the Authority in anyway Kane will possibly step in and weaken him additionally to whatever work Cena or whomever Brock may be facing at that point can do and that would essentially allow Seth to cash-in. Kane sees Seth as a weaker opponent than Brock and Kane wants the title too so why wouldn't he help Rollins get it to have a more formidable opponent than Lesnar... I fail to see where the confusion comes from, it's merely a possible booking, not rocket science in the slightest.