They never had team chemistry to begin with and their offense got by on a combination of a really good power back and the read option gimmick. Now, after the rookie contracts are over and they had to pay Wilson and Lynch serious money, they could not afford to retain the stacked roster and its really hurt them in line play. I know QBs worth a shit are in short supply so they were kind of fucked and had to overpay Wilson, but they probably should have let Lynch walk and kept more of their line intact. Also, now that they are losing, Pete Carroll's fast and loose style is biting them in the ass. The team is doing a lot of finger pointing and folks are bailing off the bandwagon. Wilson trying to Tebow it up all the time with the Jebus talk, when his wife nailed Tate on the side, probably is not helping much. Teams that are run like college programs tend to implode harshly when shit goes south, though Seattle is notable in being able to put together a championship team during their apex.
Under a disciplinarian type of coach, they probably could have sustained it longer. Sneaky Pete doesn't work that way, though. He is a boom and bust kind of guy, if you look at his coaching history.