So, who knew about this flaw, and when did they know it?

The flaw in chip design has been there since the late '90s, and then the news breaks overnight, 20 years later. If some insiders (ie: tech manufacturers, NSA, Wall Street) knew about it long before it went public, that information could have been used for insider trading or hacking. When big stuff like this happens in the financial, healthcare, or automotive industries, there are typically Congressional hearings and FBI investigations. Perhaps the IT industry should be held to the same standard.

https://www.wired.com/story/meltdown-spectre-bug-collision-intel-chip-flaw-discovery/
https://arstechnica.com/information-technology/2018/01/intel-ceos-sale-of-stock-just-before-security-bug-reveal-raises-questions/
https://www.eteknix.com/expert-says-nsa-have-backdoors-built-into-intel-and-amd-processors/