3. NSA realized that "frontal assaults" against encryption were a lot less fruitful than simply finding ways to access info once it has been decrypted.
Would have to search for the quote, but Snowden himself said exactly that, something along the lines of "Encryption works, and the NSA doesn't have some obscure 'Too Many Secrets' encryption breaking machine. But endpoint security is so bad that the NSA has lots of tools that can read messages when you do." And indeed, that's exactly what we saw in things like the Snowden revelations, Pegasus, and I'd argue even things like side-chain attacks.
Plus, I don't even know what "The three letter agencies successfully subverted the entire chain of trust" means. In the case of something like TLS root certificates that makes sense, but there are many, many forms of cryptography (like cryptocurrency) where no keys are any more privileged than any other keys - there is no "chain of trust" to speak about in the first place.