No, mRNA was suspected to be viable, but it was never proven. Like most new medical developments the early tests showed it didn't work and those needed to be worked around. Some believers did the research to make it work, but they had their detractors who said they were wasting there time as the problems weren't solvable. This time the detractors were proven wrong, but there have been other cases where more effort was put into something with no result (at least so far?)