That is irrelevant. You aren’t being realistic or practical. The US government didn’t, and couldn’t blackmail every past, present, and future employee who may come across source code or documentation or communication about a backdoor for every company that produces a hardware or software product. They also did not blackmail every independent researcher who might discover one. To even attempt this and expect it to remain a secret would be incomprehensibly stupid and we would definitely know about it by now.

There have been cases where specific things were targeted. This isn’t even close to every piece of hardware.

“There are no mistakes” is a ridiculous notion for anyone who has ever had a career tangentially related to software or hardware. I don’t know how someone who holds this viewpoint even managed to find this website. You really don’t think bugs ever happen by accident?