Because mRNA tech for rapid vaccine development wasn't available back then and it didn't spread so far that there was political pressure for expedited trials. Now it is eradicated anyway.

Part of why these vaccines were developed so quickly is that much of the preliminary work was done for SARS.

Hard to test the efficacy of a vaccine on an eradicated disease.

The is/was several SARS vaccines. They never got to phase 3 trials, because of various problems. We learned enough from them to skip all the issues this time around.

what's the incentive to work on a sars vaccine? the outbreak was contained before a vaccine was approved so they stopped work.