Thing is the science part of this isn’t rushed. They aren’t skipping steps in the testing.
Vaccines aren’t new. There has already been work on vaccines for coronaviruses. This speeds it up a bit.
It is rushed in that it is a priority. The usual lag between trials is gone. No corporate decision about whether it will make enough money to move research forward, etc. All the usual red tape is gone.
Additionally, even though the vaccine is still in trials, companies are already mass producing it so that as soon as it is cleared by FDA/UK equivalent, it can be put on the market. Huge financial risk that would otherwise not happen. Honestly this last part is huge in speeding things up