See the post directly above yours for a great answer to your questions in green. I mean seriously, it is literally the post right above yours.
I really believe Pete Carroll really wanted to keep Russell, and as a result worked hard to do what he could to keep him. John Snyder seemed to always be on the lookout for the next in line, but Pete's veto power trumped significant moves to develop a replacement.
When Russell was here he didn't make any space for a potential successor. He religiously took all first team practice reps. When he was injured he saw the writing on the wall as Geno showed some capability and success with effective play against the lowly Jaguars.
Russell came back early as the king of the QB room, and unfortunately Pete didn't stop him. Russell was nowhere near ready, but Pete was still trying to appease Russell with a belief that Russell would stay with the Seahawks.
At some point it became clear that Russell was not going to resign following this season and Pete capitulated. Pete was finally convinced that Russell was done here and let Snyder pursue a trade with his blessing.
And now here we are. With the fresh air of hope and youth and possibility. This is really an exciting season because of the opportunities and possibilities. There's no longer a stench of the limitations of incompatible mindsets between the team and one important individual.
No QB carries a team alone. The best of them know this to the core. Russell Wilson can be great, but of all the great throws he's made in his career there are ten other players that are involved in making each success possible. Russell Wilson didn't become great alone.
This is going to be a great year! Finding and developing a great QB is a long process. We have two possible redemption stories on the roster and if either cannot show the ability to learn and develop into an effective leader this year, the likelihood of bringing in the next QB to develop by next draft is high.