I'm pretty sure this all boils down to the fact that Ken Norton Jr (Raiders DC and former Hawks LB coach) probably sold him the moon when recruiting him to come to Oakland. I wouldn't be shocked if Norton pointed out that Irvin would have had x amount of sacks if he played in his defense, apposed to what Seattle runs. Which, as we all know Bruce probably shat the bed as soon as he saw numbers like that thrown around, with the guarantee of much more money. I don't hate Norton for selling on Oakland, as that is his job now. Nor do I hate Irvin for leaving, you would be crazy to not take the money when it's offered in a game where you are literally one play away from major injury or never playing again.
I guess what I don't personally understand is, why would he fell the need to take any kind of shots when leaving? Even if you really think and/or know that you will put up better numbers in Oakland than you did in Seattle, why say anything at all? It seems like some players, no matter how many wins they have while on a team or how successful they are, they still seem to be all about themselves. Maybe he's upset that Seattle couldn't give him a proper offer so he's going to take shots on the way out, that's really the only thing I could think of. Perhaps players still don't realize that no matter how much the team wants to keep a player, the cap will never allow it, ever. For a league were players always seem to say "it's just a business", a lot of them sure seem get their feelings hurt and feel the need to say something on the way out, although, I may just be looking in to this too much.