The team at facebook will be able to show bigger sales, making the next version more likely. You will count as a "oculus quest user" in steam stats etc. Developers will be more likely to support this headset. Etc etc etc. The market is still so small that network effect like these can be huge.
Facebook is selling at a loss in an attempt to destroy the competition and build another monopoly. They don't care if they don't make a profit now, as they will be able to gauge you later.
Luckily, there are laws against monopolies. I don't see what you mean by Facebook currently having a monopoly, because Facebook is not the only social network.
Given the fact one of their main competitors is Valve, I don't think you have to worry about them destroying their competition financially either. Facebook isn't even really competing with them, FB is going for the low end market.
And the judge seems to disagree according to the article you linked. I really just don't see it. Hacker News, Reddit, 4Chan, Discord, youtube and tiktok all are social network that don't belong to Facebook. I can't see how the government will ever win that one. From my point of view Apple and Google are much more monopolies.
