I disagree. It's also what allowed the "IE-only web" to persist for about five years.
It might have been a good thing until about 1997, but at that point there was no shortage of people creating new web content, and raising the barrier to entry would have done no harm. And a lot of innovation in browser features might have happened sooner (due to increased competition between browsers.)
There was great competition between browsers through the 1990s. Unfortunately, they were competing through 'value add' proprietary extensions and browser lock-in, which is orthogonal to the issue of whether HTML parsing should be more permissive or more draconian.
Somewhat. Microsoft reverse-engineered a lot of Netscape's rendering quirks, as well as adding their own. Being quite liberal it what it accepted certainly didn't hurt IE adoption. (And a lot of these things are now in black&white in the HTML5 spec).
"[W]hy do we have an <img> element? Why not an <icon> element? Or an <include> element? Why not a hyperlink with an include attribute, or some combination of rel values? Why an <img> element? Quite simply, because Marc Andreessen shipped one, and shipping code wins."
It might have been a good thing until about 1997, but at that point there was no shortage of people creating new web content, and raising the barrier to entry would have done no harm. And a lot of innovation in browser features might have happened sooner (due to increased competition between browsers.)