You could be right with your above assessment though we probably will never know. My thinking is that they had to have more than one option for 5 before a trade down, and going too plan C. They likely were unable to find a trade they liked though.
Lots of very interesting choices left for DLine guys, undoubtedly they'll surprise us and our preconceptions about draft needs and player abilities. I do believe though high football character will be a key factor with every pick and players with character questions will not likely be fits anymore.
Educated speculation ahead:
There might've been a contingency in there, like scenario Y, to have all of their bases covered. But Seattle has/had the draft ammunition to get their Franchise QB if they truly loved a guy in this draft. They might've liked Richardson, but they did not love him enough to go get him.
#1 Young
#2 Seattle moves up takes Richardson.
#3 Houston moves up takes Stroud.
#4 Houston moves up takes Anderson. Indy missing out on their guy willingly trades down.
A scenario such as this would've played out had Seattle really loved Richardson. Or they just would've beat Carolina to the punch and traded with the Bears for the #1 spot and had their pick of the litter if they truly loved these QBs.
Richardson has to be used like an RG3, Lamar Jackson type to be effective, and is the biggest gamble in this draft.I don't think Seattle is interested in a run first QB.
I think they liked Young, Stroud, and Levis tepidly. Young who plays like Russell Wilson, and Stroud who plays a lot like Geno Smith. Levis who plays like an untamed Favre. Seattle likes guys who are accurate and can play QB, but can also run when things break down. Richardson is not that guy, he is a massive project that has to be used as a runner if he plays early, and it may never come together for him due to lack of experience.
Seahawks fans will be thanking their lucky stars they didn't take any of these QBs with the 5th pick in a year or two. Most overrated 1st rd QB class of all time outside of the '21 class.
That would be the: Trevor Lawrence, Zach Wilson, Trey Lance, Justin Fields, Mac Jones class.
Paying Drew Lock very good backup money was a tell they didn't like these QBs.