Everyone focused on Microsoft at the time but Yahoo and others also dissented. I think for good reason; ES4 is nearly completely different from normal Javascript (static types, class-based inheritance).

Also Adobe was getting a standard that was what they already had and Mozilla had a AS3 VM runtime from Adobe. Microsoft would have been starting from scratch. I don't blame them for blocking it.

(EDIT: If you look at this Apple also marked red to much of ES4: http://spreadsheets.google.com/pub?key=pFIHldY_CkszsFxMkQORe...)