Basic overview of FDA process:

https://www.fda.gov/drugs/information-consumers-and-patients-drugs/fdas-drug-review-process-ensuring-drugs-are-safe-and-effective

Pfizer did not do all the animal trials. They lumped Phase I, II, and III together rather than individually. They did not take the "several years" needed, but just did a trial for 28 days.

There really isn't anything they did that was within the usual FDA process.