What “saved” Apple was the iMac in 1998, not Microsoft.

Microsoft bought $150 million in non-voting stock in Apple as a show of good faith. Apple made Internet Explorer the default browser for the Mac and Microsoft committed to Office for the Mac. At the time, Internet Explorer 5 for the Mac was the best browser on any platform.

After the 5 year period, Microsoft sold those shares, making a huge profit.

At the end of the 5-year agreement, Apple shipped Safari 1.0, based on the KHTML codebase and the rest, as they say, is history.

Ironically, Microsoft's browser is now based on a fork of the engine of the browser that replaced IE on the Mac back in the day.

Well there was the legal battle going on between the two as well. So you could think of IE, Office, 150M stock was part of the package.

This is a myth. Apple always had massive amounts of cash even at their low point when people considered them worth barely more than their cash.

That move alone (plus Bill Gates' appearance at an Apple event) might have saved the platform, not only by making it more attractive to users, but also by giving the platform more credibility with larger enterprises.