Knowledge about this type of attack dates back to the 90s (possibly earlier), but it isn't entirely clear whether the engineers who developed the "protection check after [speculative] load" were aware of that. I would argue though that "check after load" should have smelled bad to people intimiately familiar with CPU design.

It should be noted though that at the time neither sharing processors with strangers / across trust boundaries nor executing arbitrary crap in a VM were common activities. Memory protection and such were mostly viewed as a technique to increase reliability, not to provide actual security.

I want to say I'm not giving them a pass but I think you can go overboard and "know" that "hey in theory someone could" and security yourself into never doing anything.

Accordingly how much they knew about the nature of it and their ability to predict is really the question and IMO kinda a hard one to know (unless there are some memos out there) / judge.

Granted in the age of little to no consideration given to security in so many places .... I wouldn't be surprised by anything.

Working closely with Intel and others on these issues I have seen zero evidence that anyone realized the security implications and shipped anyways. Zero evidence.

This bug was designed around 1993 when security, multicore, and SMT didn't really exist.