As far as I remember the debate about the max block size cap started a "long" time ago,
an it risked to stall indefinitely.
In my opinion Gavin's conduct has objectively an accelerating effect on the decision
process. I dare to say that such "extreme" attitude had stimulated a lot devs
in focusing to find a solution and to come to a compromise.
I'm not saying that his proposal is perfect or better than any others on the table, just
stating that his strategy have moved the situation toward a new equilibrium by a long shot.
I agree. Gavin's threat of a unilateral hardfork
did successfully concentrate minds on coming up with solutions to the problem.
How do you know that his intention was not to stage a dev-team coup? He behaved exactly as if he really intended to, nothing suggested otherwise (although I don't claim to be aware of every bit of public commentary Gavin has made, as previously mentioned, I am not a twitter user

)
I don't know as any other person who based his opinion on fact. I can for sure observe public community reactions to Gavin's behaviour, though.
Well, the facts are that Gavin literally did just that; an alternative, hardforked client with a 20 MB block limit, and anyone from the core deve team that didn't like that could watch while he lobbies miners, services and merchants to accept the new client. That was what he said, he has not retracted it, nor confessed the ulterior motive you are affording him. Those are the facts, are they not?
Sure facts are facts, while speculation is another thing entirely.
Gaving did something and community at large react to his stimulation.
And I prise community reactions, in particular core devs reaction.
From what I can see we're moving forward in the process of finding
a way to make bitcoin scale.
Just to make an example in the beginning of the debate a lot of devs
(core or not) did not acknowledge that a block size increase was needed
Now almost everybody, modulo mircea popescu and mpex group, agree
about some sort of increase.
This is a result of Gavin action, and I say a positive one.
Other less measurable, but nonetheless actual result, is the increasing pace
at which "layer 2" solutions are developed (Lightning Network, Sidechain, Payment
channels implementations etc etc).
Mind you I never said that Gavin's proposal are the best available technical
wise, I don't have enough knowledge, skills and time to make a proper judgement.