1.) Proprietary UNIX vendors. Cheap workstations? Fuck you. OS without a support contract? Fuck you. First party compiler? Fuck you. These started to improve after 2000 with ports of open source tools, but most people would realistically be in way over their head price-wise unless they were accessing these systems through a university or workplace.
2.) Open source UNIX and UNIX-like systems. Linux was still pretty rough around the edges, and BSD derivatives were still pretty widespread. All said and done, you had to know these existed, know how to be involved in the community, and deal with the reality that the money just wasn't there yet. These options were not without compromise -- it would be years before Linux began making inroads in the "serious" deployment market.
3.) Microsoft. They did shitty things, but it was possible to get affordable development tools on affordable (and actually quite performant, all things considered) hardware, instead of needing tens of thousands of dollars for option 1 or being in the right place and time for option 2. Windows, VB, etc. causes lots of moaning and groaning today, but it had to have been magical at the time.
Give them all a try on period accurate hardware, one after another. You will become acutely aware why people put up with Microsoft.
In the 2000s, getting linux to work with wifi was a mess of command line commands and other PITAs that no normal users would put up with.
If you want to focus on just his business, initially, Gates was a tech hero, upsetting the incumbents as much as any modern disruptor. His company came to be known as a villian, was itself upset, and is going through a reinvention period during which I think they are doing really good things. But none of that should be about his character. He played the game and won, then got out and focused on more important things.
Corrected that for you.
In all seriousness: I think Bill Gates is probably sincere in his philanthropy, but that the reason is emotional maturity and reflection... that and he's sitting on a fuck ton of money that one man can only squander if not put to better use.
What gets me is people who so vehemently hate that they talk about killing the person, not the business.
Are we going to applaud Zuckerberg in 20 years when he's going to use his money for good? He could already be doing good right now, instead of being a net-negative to the world, but he chooses to make billions instead.
You forget that outside of tech everything that MS did that we rail on about will be remembered as good business. Nobody except people on the inside have these idealistic views about software and freedom and all that.