These three companies are also all very different as businesses. Their biggest commonalities are the people they hire and where they're located. After that, they look pretty different.
https://news.crunchbase.com/news/heres-who-has-gone-public-i...
The IPO process takes a while, so is it really that surprising that a bunch of companies might have overlapping periods of IPO activity?
If a bunch of companies in the same sector, that compete with each other, went to IPO around the same time, that might be a _little_ weird, but this is largely just a coincidence. AirBnB has been anticipated for a while, Palantir needs the cash, and Corsair, well, I dunno what's really up there, but they're gonna try to IPO too. Either way, it mainly seems like a coincidence for these three.