[dragonwriter]

> Anyone with who has taken AP Biology could conceive of and understand the idea behind making vaccines rapidly: take some mRNA, inject it, have in translated as the antigen in the body.

There was quite a lot of development on basic techniques of working with RNA necessary before that could even in isolated circumstances be easier than, or even competitive with, “isolate the antigen, inject it, done”.

> The question is, how did this start just now?

It didn't.

Getting a treatment to market isn't the start of application of a new technique in medicine; its usually something that happens many years, often decades, into work using the technique.