Their benefit was they weren't required to conduct the normal, lengthy trials that generally come before FDA approval. Trump authorized the FDA to give emergency approval to vaccines, including the Pfizer vaccine. You do realize they benefitted from emergency? approval?
There is a lot in here that isn't correct. First, the drug makers are required to conduct phase 1, 2, and 3 trials to apply for EUA. The evaluation time between trials my be compressed, and the phase 3 trial doesn't have to be completed prior to application for EUA, but it does have to be ongoing while meeting certain thresholds. FDA expects (I think) a two month threshold for greater than 50% of phase 3 trial participants prior to application with the rest of the data being available during the evaluation process, but they didn't, and can't, forego phased trials prior to EUA.
Second, FDA received authorization to use EUAs in 2013 when the law was passed. All they need to enact it is a declaration of emergency from any number of gov agencies or imminent threat from homeland security. In the case of Covid, Azar declared an emergency in February. FDA then used their authority to grant EUA for multiple tests, treatments, and vaccines. This has been done for H1N1, MERS, Ebola, and others.
Third, there is no emergency approval. There is approval, and there is Emergency Use Authorization. The Pfizer, Moderna, and JnJ vaccines received the latter. To gain approval, they would go through the BLA process after completion and analysis of the phase 3 trial. This can be a lengthy process, and this is the most significant time savings afforded by the EUA.