Indeed, they were the exact opposite: huge multinationals with presumably gigantic legal, infosec and HR policy departments who could probably jump through the various compliance hurdles required by this procurement process in their sleep.
By comparison the startups you're complaining about usually take years to reach sufficient maturity to take part in large public sector procurement processes like this.
Clearly in this case maturity and scale were not a bulwark against incompetence, opacity and mendacity. Indeed the opposite - as I type this the Post Office's lawyers Herbert Smith Freehills are making mealy mouthed justifications for witholding reams of technical evidence from the public enquiry for months. It's disgusting, and as someone running a small business and endlessly having to justify our commitment to information security, data privacy and transparency I find the hypocrisy infuriating.