I think that's another case of assuming bad intentions. Once Microsoft had a slightly differently behaving version of JavaScript that was in use by
hundreds of millions of people, including many enterprise environments with internally developed and bought solutions that
required Internet Explorer and it's version of JS and ActiveX to function who more often than not were also large Microsoft customers, the idea of breaking all the existing functionality just to be compliant with a standard becomes a non-starter. Were there people in the company that liked this situation? Probably. That doesn't mean it had to come about through malice. It's easy to see how a similar situation with Chrome or Safari could occur if they had greater than 90% of market share.
The only reason we are where we are today is because there's much less of a single dominant player in the browser space, so using standards are incentivized.
P.S. Yes, MS got their market share through shipping the browser with the OS. While it may have led to a monopoly in the browser space (or close to a monopoly, depending on how you want to look at it), I think it's hard to say any one of us wouldn't have made the same decision to bundle them were we in the position of selling the OS and also putting out a browser.