I still haven’t understood Microsoft‘s strategic rationale for being the leading provider of a free browser.

Google and Chrome makes sense because they need as many people browsing as possible.

But IE for MS? How was it supposed to help them?

I was around for all this. Things were different back then - in my opinion, considerably worse.

Gates wanted a locked market (for himself/Microsoft, of course) on ALL personal computing. Back then MS-DOS', then Windows', market share was practically 100% (or at least 80+%).

The next step was to dominate the apps, which led to effectively proprietary file types for the documents, spreadsheets, etc in Microsoft Office applications. This prevented competitors from opening and/or editing MS file types in their own products, stifling any new approaches to these standard business applications.

At this point, things were very rosy for Microsoft, and it was generating huge profits from these locked-in markets.

Then came the rise of the consumer internet, threatening MS' cozy applications world. Distributed client-server applications over the internet would be a nightmare (i.e. threat to the profit machine) if Gates' MS couldn't gain a handle on them. So Gates made sure there was his Internet Explorer included on every machine he controlled so that he could build in proprietary handles and functions that other browsers couldn't emulate.

I suppose the rest of the story is a little more apparent to us.

Netscape announced that they were trying to kill Windows so of course Microsoft had to prevent that by any means. It was justifiable purely on a defensive basis.