Would Microsoft not exist without open source project? Microsoft is that company founded in 1975, but the GPL license only appeared in 1989, and BSD licenses appearing at roughly the same time just because of the Unix Wars.

Big tech companies can easily hire manpower to make proprietary versions of software, or just pay licensing fees for other proprietary software. They don’t rely on open source. Microsoft bought 86-DOS to produce MS-DOS; Microsoft paid the Unix license to produce Xenix; and when Microsoft hired former DEC people to make NT, it later paid DEC.

Instead, modern startups wouldn’t exist without open source.

I think they would due to massive financial incentive. On the other hand, a lot more developers might actually be getting compensated for their work, instead of putting their code on the internet for free and then complaining on social media that they feel exploited.

it's the exact opposite but alright, take a look at who's behind funding and sending code to the linux kernel if you want an example

And a gentle reminder that most of open source you use was developed and is maintained by tech companies.

Take a glance and contributor lists for your projects sometime.