Wait, you're telling me Vince had the storylines with Road Dogg and Chyna already written out and he still agreed to jump ship? He must have really, really hated WCW.
Both him and the Giant left WCW for way less money upfront and more dates they had to work, admittedly with higher upsides.
Look at it this way, from 1998 on the only people who signed with WCW were the ones who for the most part weren't part of the company. Almost everyone who was working for them and had the chance to sign elsewhere did. Hell Raven could have smoothed over his problems with WCW and instead chose to take ten times less money to go back to an obviously dying ECW. Benoit left even though WCW was going to double the money the fed offered.
Giant and Jericho were canaries in the coal mine.