Presumably someone did, but it would not at all be unheard of for due diligence to not be particularly diligent at all and for later investors to then trust to the diligence of the earlier ones, as after all, being thoroughly diligent is exceedingly expensive and why double up when someone else has already checked...
I would agree that you usually do not raise that kind of money without reasonable DD, but there are more than enough counter examples out there of people bullshitting investors out of very large sums, both deliberately and through deluding themselves.
That does happen but less frequently than you probably think. In this case there was a company with a track record and a bunch of tech which could be audited, that's a relatively straightforward affair. It gets a lot harder in early stage 'virtual' (as in: no physical product) companies.
Good find! I'm curious what their long term plan is, if they're going to stay private or IPO at some point. If they IPO you can expect a lot of information to become more widely available than it is today.
I would agree that you usually do not raise that kind of money without reasonable DD, but there are more than enough counter examples out there of people bullshitting investors out of very large sums, both deliberately and through deluding themselves.