Diversity and multiple implementations are essential for the web IMO.
V8/Blink/Chromium are not independent community projects, but firmly in the hands of Google. Chromium being the only viable implementation would put too much control in the hands of a single company (regardless of which company that is, Firefox being the only implementation would be just as bad).
It's redundant effort, but it also enforces consensus building and exchange of ideas.
EG Google would have happily stuck with PNacl, but (afaik) Mozilla pretty much forced their hand - with the result being Webassembly, a much better design.
If that diversity doesn't lead to better results then it isn't necessary. I wouldn't consider the oligarchs of Js engines to be diversity, nor inherently innovative. In the past there has no doubt been innovation, but currently it has significantly stagnated.
Wasm was not what was promised. Mozilla and the other vendors just translated the wasm bytecode to js bytecode. All it did was skip a few steps. Yet the actual requirements for performance, simd, was ignored in its proposal. It has been a significant under delivery overall.
If they were innovating then spidermonkey would be comparable or better than v8. It isn't. It's effectively proprietary to Firefox. Id call that the opposite of diversity.
V8/Blink/Chromium are not independent community projects, but firmly in the hands of Google. Chromium being the only viable implementation would put too much control in the hands of a single company (regardless of which company that is, Firefox being the only implementation would be just as bad).
It's redundant effort, but it also enforces consensus building and exchange of ideas.
EG Google would have happily stuck with PNacl, but (afaik) Mozilla pretty much forced their hand - with the result being Webassembly, a much better design.