I think today's web developers are just a lot younger. I'm 21 and I came to start developing when IE6 was still relevant. (Around my age 15). The generation after me came to developing in a completely different post-IE6 world. I don't think most of them realize the historical context or even the relevance. It's a vicious cycle. I'm not sure if there will ever be a cure for young naivety.
These literal kids just want to build cool stuff and they have more power/freedom/resources than ever before. Give them time and the good ones will learn from their mistakes.
- There was diminishing market interest in supporting alternatives to Windows because non-windows marketshare (Mac OS X, UNIX workstations) was plummeting. This allowed Microsoft embrace-and-extend to succeed.
- The web development field was nascent at best. Similar to how many web developers are moving into the mobile space today (and bringing their ideas of how to write apps with them), you had Windows-centric enterprises migrating towards writing web sites (not apps!) and bringing their ideas of how to do so with them.
I very much doubt that the web browser war would happen again in quite the same way. Between the availability of open-source browser stacks, the genuine viability of multiple platforms and vendors (iOS, Android, Mac OS X, Windows, and even Linux), and the established web development community (which would have to be co-opted), I don't think it would be quite so easy for someone like Google to 'win' a browser war and then stagnate indefinitely.