No one had to be told to start developing vaccines. Every single company out there looked into whether they could try or not.

Trump streamlined the government part so that they wouldn't be so much on the way as they normally are. On top of that they have the guaranteed contacts if they were approved, on top of that fm gave guaranteed contacts so the companies would be willing to do the research and development in one continuous run. Otherwise they usually do at every point in the development to make sure it makes financial sense to continue with the next stage.