Microsoft in 1999 was not the same company it is today and did some very unethical things. For example:

https://www.itprotoday.com/windows-78/ibm-microsoft-warned-p...

Other articles report that computer producers were given Windows "for free" as long as they did not offer nor support OS/2 on their hardware. Microsoft applied this practice for a few years and indeed lost income by giving Windows for free, but it ensured that the regular user never heard of OS/2 and then when IBM gave up the situation changed. Besides, Microsoft would still make money from Office and other products.