That's a combined 400,000 employees out off a job in one day. I wouldn't wish that hardship on those people all of a sudden, and that's before we consider the wider ramifications to the economy from those people being unemployed. Then there's all the people and companies, non-profits and NGOs that use theiur services which would run into major problems.
I would be be tempted to think perhaps you just glossed over that, because the alternative appears to be a complete lack of care for others, but as you've noted you've thought about it. Carefully.
giving people tools like Word/Docs, Excel/Sheets, etc that they can use to express themselves and calculate things? Providing email for people? Giving people "it just works" (albeit not as well as Apple's stuff) operating systems (Windows/ChromeOS/Android) that they can use without having to deal with the complications of getting Linux working (although you could argue in recent days Ubuntu does this as well)? VS Code? Creating widely used programming languages (C#, TypeScript, Golang, Dart)? Paying people to work on open source projects? Google search, which, while far from perfect, does still enable people across the world to easily access information that is useful to them?
Would the income currently going to Apple, Google, Amazon and Microsoft for various services be better off going to 10,000 businesses employing 100 people each? That would give more choice, equal number of jobs and a stronger middle class
I think you're missing the point, which is that to make such a change in a day would be chaotic and problematic. I'm not saying Microsoft and Google need to stay, I'm saying that it's not something that could change overnight without extreme hardship caused to many people. It's not just the change, it's how it happens. Many more people are able to work from home now than a few years ago, but I doubt most people think the cause of that was worth it. Do I think we'd all be better off with less mega corporations and more SMBs? Yes. Getting from here to there in a way that makes sense and doesn't cause major problems is important I think though.
Either the person I replied to above was being flippant and callous in their wording in a way they should have been aware of if they thought carefully about it, or they didn't think all that carefully.
I would be be tempted to think perhaps you just glossed over that, because the alternative appears to be a complete lack of care for others, but as you've noted you've thought about it. Carefully.