Re: "consumer device manufacturers"
"We just discovered a vulnerability in a raft of CPUs that dates back more than a decade and nobody had a clue."
Nobody had a clue?
I seriously doubt that is the case.
See the flaws in the Intel Management Engine, their implications and consequences.
It's a long albeit interesting read.
And then see if you can, with all the good faith you could possibly muster, say "nobody had a clue" again.