Microsoft has continuously attempted and failed over multiple decades to get Windows NT of any flavor or configuration certified against anything more stringent than EAL4+ which is not even certified to protect against attackers with a "Moderate" attack potential. A older version of the standard prefaced EAL4 as being limited to protecting against "casual and inadvertent threats". That does not, by any measure, qualify as a vote of confidence in the security of the product. Under the old Orange Book standard EAL4 would approximately qualify as level C2 as Windows systems contemporaneously certified against both the Orange Book and the Common Criteria were certified at EAL4 and C2 simultaneously. A post-mortem on the Orange Book evaluation criteria [1] clarified that C2 was designed to allow commercial systems with no security to get used to the idea of doing a certification so that they could in the future design a proper system with actual security [2]. To add insult to injury, Microsoft has only ever achieved these levels with stripped-down, hardened versions so they could only achieve such vaunted heights as "protection against attackers with a Enhanced-Basic attack potential" after security configuration.

Also note that EAL4 is the level pointed out in the Common Criteria as being the highest level a existing commercial product can be retrofitted to. The standard explicitly points out that to achieve a higher level requires a greenfield redesign with security designed to achieve higher levels from the start (hint hint they added that in because Windows kept failing in their attempts to get their EAL4 quality system certified at EAL5).

Maybe you are correct that security was considered during the design process of Windows, but the security designed in is nothing short of a complete and utter joke. No security professional of any competence at designing systems that can actually protect against skilled adversaries would stand behind their security pedigree. I mean, for gods sake, even they would not stand behind their own security pedigree; find me one person on the Windows development team who would dare declare that Windows can survive against a NSA penetration test. It is laughable just thinking about it.

As for their ability to sell to the government. The total incompetence of the entire commercial IT world is so complete that under pressure to allow COTS vendors to make billion dollar deals with the government the procurement standards were lowered to allow EAL4 systems in high security contexts (as long as they were never connected to the internet, thank god for small wins). It has actually regressed even further in the recent years as in recent years they lowered the standards further to allow commercial firewalls and antivirus systems which are generally only certified to EAL2 under the swiss-cheese theory where if you just stack enough systems with egregious holes together then the system will be secure. We can see how that is working out. It is now to the point where now they just allow anything that is "certified" at any level.

That every commercial IT system is at best EAL4 quality is part of the reason why everything is so horribly vulnerable these days. The world runs on systems certified to absolutely not protect against "moderate" threats. To rise above that we must use systems that are designed for real security from the start as we have already seen from history that none of the existing systems can be retrofitted to do so.

[1] https://www.stevelipner.org/links/resources/The%20Birth%20an...

[2] https://www.stevelipner.org/links/resources/The%20Birth%20an... Page 6, Column 2