I think the point with that was that those who needed to know didn't know because they hadn't been presented the data in a meaningful way.
So you are correct that he knew, but you are wrong in claiming the lecturer got it wrong. It is exactly because those who makes the decisions don't have the necessary know-how that visualizing the data in a meaningful way is so much more important.
The decision makers have a very, very strong incentive to keep things going. And the PR circus surrounding the teachers made it worse in the Challenger case. Meanwhile, everyone else has a strong incentive to shut the hell up.
Besides, saying the engineers didn't "try hard enough" is essentially claiming the engineers were in charge. They were not. Managers are paid to manage their department, not just please the higher ups. When a claim is made that failure to address a problem will result in catastrophe and loss of life... really what more needs to be said, or drawn, to make the point? If you're not going to trust your own experts, why have them at all?
And how does the Challenger explosion in any way suggest that there aren't enough engineers? Certainly this one major issue had engineers urging for delay, so there doesn't seem to have been a lack of them.
You know that all of the shuttles risks are well documented, right? It's a mountain of issues that basically gets the "ok to be ignored for now" stamp at every launch.
After reading Feyman's account, I believe that no amount of visualization nor compelling case making would have made any difference.
1 in 100,000 means launching the shuttle 3 times a day for nearly 100 years and experiencing only one failure. If the logical side of their brain is that far out to lunch, why would you think that the problem was simply an insufficient appeal to logic?
Visualization is not as such about logic, its about interpretation and communication.
So the problem was more about insufficient appeal to emotion than to logic. Whether that would have been possible in the case of Challenger is another question, obviously retrospective analysis is always easier.
But in my mind there is no doubt that visualization are able to change peoples opinions and understanding. I have seen that first hand on some projects.
So you are correct that he knew, but you are wrong in claiming the lecturer got it wrong. It is exactly because those who makes the decisions don't have the necessary know-how that visualizing the data in a meaningful way is so much more important.