I don't know where this notion that Welker wasn't productive as a Dolphin when the Patriots stole him away. Yeah he didn't have a massive season before leaving the Dolphins but his production on a joke of an offense in 2006 was in the same area as name receivers Marty Booker and Chris Chambers who were both former Pro Bowlers who started the year as offensive centerpieces...heck Welker even led the team in catches. This is a guy who was brought in a few games into his first season as a returner specialist who wasn't even really getting run with the receivers at all his first year, and scarcely the second. His tenacity was already apparent from his return game, and he showed he could be an impeccable, tough, and sure handed route runner in 2006. He was clearly a player on the ascendancy and there was no reason to think that he wouldn't continue to improve and produce at a higher level.
If you couldn't imagine how an impeccable route runner who grabbed 67 balls from a gimpy Daunte Culpepper, broken Joey Harrington, and NFL Europe caliber Cleo Lemon could catch 110 balls on the best coached team in the league with a top shelf QB in a system that showed they could produce even with second rate talent at the receiver position, that's on you. Because I could fully imagine it happening and expected it. (Similarly, I don't think many people account for a decrease in production when a 110 catch guy leaves a situation like Manning or Brady-led offense).
Fact of the matter is after that going from the Saban debacle to the Cameron era was one of the lowest points of this franchise. We even traded the fricking punter. Most new NFL head coaches will get rid of a lot of talent they imagine they'll replace with "their" guys but ultimately fail and get fired, and Cameron was one of the absolute worst examples of that. Letting go of Welker was just one of a number of controversial and ultimately unsuccessful roster moves he made. Ultimately Welker was the only one really on the ascendancy, but letting the rest of them go wasn't a good move at the time. It resulted in a team so laughably bad it makes me sad I ever lived through it.