If most countries weren't doing lockdowns all over the world to the tune of billions of dollars lost - the incentives for developing vaccines so quickly would be much smaller.
Giving a grant for 10 million dollars to 10 companies that might have a shot at developing the vaccine is one thing. Banning almost all business worldwide till the vaccine is developed redirects almost all the money in the world towards developing that vaccine.
If governments banned fossil fuels ignoring the economic consequences for a few years - we would solve global warming no problem. The alternatives would get developed in record time because of how much money they would be immediately worth.
But the suffering in the meantime caused by the regulations don't seem as justifiable in case of global warming as it did in case of Covid lockdowns, so governments won't do this for global warming (or at least - not until people start dying of global warming in big numbers).