Then why not an inactivated viral vaccine instead of stimulating the body to produce artificial spike protein?
I don't know. That approach clearly doesn't work with all viral diseases else we would have vaccines for more of them. It's also true this is the first successful coronavirus vaccine we've developed which tells me the most basic approach doesn't work for some reason.
I'm sure if Pfizer could have developed a vaccine for 1/50th of the cost they would have.