i believe that "what they knew" was that rubella is known to cause CRS (Congenital Rubella Syndrome)

https://en.wikipedia.org/wiki/Congenital_rubella_syndrome

and that CRS was known to manifest as ASD (Autism)

therefore if you can prevent rubella, you can prevent CRS, and thus prevent ASD...

which is exactly the point the study is trying to make.

but then, in the course of trying to prevent a few rubella infections, they accidentally caused a whole lot of immune responses to rubella.

and its the immune response that causes the problem.

the easiest way to think about this is fever.

infections don't directly cause fever per se, but rather they trigger an immune response, which is the fever.

fever is how you can tell your vaccine is working!

by the time they figured out they were doing more harm than good, it was too late to come clean and admit it, so they just keep lying, and deny, deny, deny.

and blame ASD on 'genetics'.

which is why they don't trumpet the above study from the rooftops

ATTENTION: Rubella Vaccine PREVENTS Autism! Vaccinate Your Crotch Goblins TODAY!

because all that does is open the door to ask how a vaccine prevents a supposed "genetic" problem.

once people understand the mechanism by which rubella infection causes autism, its not hard to figure out how rubella vaccines cause autism too.

ironically enough, autism used to be "rarely" caused by natural rubella infection, but today autism is "commonly" caused by rubella vaccines.