All these new technologies, the techniques, the principles were in development since years if not decades.

Not trying to diminish the accomplishments achieved, great effort nontheless. Just saying nobody started from zero here, that would have been insane and frankly impossible.

Yes, I first heard about intramuscular nucleic acid injection around the year 2000. At the time it was naked DNA and not RNA in a lipid nanoparticle suspension, but the principle was the same.

They might be working on this particular vaccine since 2020, but AFAIK they have been working on the specific principle the vaccine uses since 2008.

If we could somehow develop rapid testing in some way, it's shocking to me that the vaccine could have entered mass production by the Summer.

There was a time where the only true way to test a new model Aircraft was to build one, but nowadays pretty much every characteristic is well understood by the time it enters service. To reach a similar point with vaccine testing will be important when the next pandemic hits.