As you acknowledge, the branding is almost nothing to do with the publisher itself though. Nobody cares a jot that journal X is from publisher Y (I don't even know who publishes most of the big econ journals I read papers in).
The 'branding' (and I think most academics would prefer the term reputation) is developed over many years by good decisions on the part of editors and reviewers — generally academics working for free — and by others making citations. The publishers contribute negligibly to this, which is why the substantial rents they subsequently extract — and the exclusivity of knowledge this promotes — are so annoying to people.
Well, for what it's worth publishers are responsible for maintaining those editorial boards, over time periods much longer than academic careers. They care about the long term sustainability of the journals for commercial reasons, of course.
The 'branding' (and I think most academics would prefer the term reputation) is developed over many years by good decisions on the part of editors and reviewers — generally academics working for free — and by others making citations. The publishers contribute negligibly to this, which is why the substantial rents they subsequently extract — and the exclusivity of knowledge this promotes — are so annoying to people.