I'm a bit of a younger Browns fan - I became aware of the Browns in the late 80's (oh joy). While I can't speak to the impact of some of the moves you referenced, I don't agree that moves that far back killed the Browns.
People forget (and I think Browns fans took for granted at the time) how good the 1994 team was. 11-5. Won a playoff game. Had what turned out to be a future HOF head coach. Had one of the best defenses in the league under Nick Saban. Had a solid QB. We all hated the QB and the coach because they unseated Bernie Kosar, but in hindsight it was the right thing to do.
The following year the Browns were down a little, but not out. Nick Saban had left for Sparty in the offseason - perhaps that was part of it. They were 4-5 when Modell announced he was moving the team. They limped to a miserable finish from there. This wasn't a terrible franchise that Modell packed up and carried away. They were a relevant team, and if Modell hadn't let all the air out maybe they don't lose six of seven games down the stretch - maybe they qualify for a wild card spot in '95 and maintain some of the momentum they had captured the year before.
You won't catch me saying that if they had stayed they would have won a Super Bowl like they ended up doing in Baltimore. Heck, if they had stayed they may not have even been in the right draft position to pick a guy like Ray Lewis. Plus, I know Cleveland sports well enough - I know better than to think of that as a possibility. However, the pieces were in place to remain a vital and competitive team going forward from that point.
To me, if you have to look back and point to some kind of foreshadowing event that took place ahead of the move that points to the current state of affairs in Cleveland, it would have to be the the replacement of Bernie Kosar. Kosar was on the decline, Testeverde was on the ascent, but we hated Belichick for making the move and hated Vinny for being the guy who took Bernie's spot. As fans we didn't handle it with any sort of perspective and it points to the way the fans and the team have reacted to the QB position with the new Browns. There's no patience on the part of fans. There's desperation on the part of coaches and GMs. Nobody commits to a player they believe in or a philosophy for how the team is to be assembled and run.
At this point, that's the thing I'd like most to see changed. Hardly anybody with the Browns (coach, GM, QB, etc.) has received more than a half-chance ever since the team was brought back. Despite being in a constant state of rebuilding they haven't even fully committed to that - they haven't been able to get the No.1 overall pick in a decade in spite of their sustained miserable state. I'm becoming convinced at this point they need to stick with the current personnel - give them more than a half-chance to be successful. If they are not successful, at least stick with them and commit to tanking and doing an proper rebuild instead of the perpetual triage that has become a way of life for the new Browns.