The trials for mRNA vaccine for SARS were scheduled to start in 2020. Because of the Chinese scientist who posted the COVID-19 sequence, they were able to substitute the RNA sequence. I was concerned about the rapid rollout until I learned that this project had been going on for a decade
Moderna in fact had a platform and phase 1 trials for Zika completed but then interest fizzled out when Zika fizzled out. IIRC that's why the FDA had Moderna on speed dial. "Remember those folks who did the zika vaccine?"
But "stay away from each other while we complete the most ambitious and accelerated phase 3 trial in history" was not an unreasonable request. (The only reason the trials got to their endpoints so fast was that people ignored this advice).
The novel thing was the mRNA platform and I think the specific antigen was relatively easily swapped in and out. The research on SARS-1 spike did give researchers a significant head start in guessing which spike antigens to use for SARS-2
And the platform was (and still is) being actively developed as a cancer therapeutic. Bancel took a huge bet to pivot the company’s focus to COVID vaccine production.