I know nothing about vaccine development, but I'd guess part of the answer is "It mattered."
People try way harder when the stakes are high, and everyone involved is at least a little terrified of being "the one who delayed it." That does wonders for cutting through pointless red tape and bureaucratic delays.
A minor example:
About ten years ago, a flash flood completely destroyed about thirty linear feet of the main road connecting the tourist district of Hershey, Pennsylvania to the rest of the town.
I assumed it would take weeks or months to repair, based on how long road work has usually taken in the area. It would have been a disaster for a lot of the local restaurants, economically.
IIRC, two days after the flood the road was back in order. It certainly didn't take more than a week.
Obviously, inventing a new vaccine is orders of magnitude more complex than fixing a road, but I think this aspect of human nature still applies.
This was the main interstate connecting the suburbs to the business districts in Atlanta. The traffic on alternate routes after the collapse was apocalyptical. However, the new replacement was built in record time (1 month). The teams were given cash bonuses and other incentives to finish ahead of schedule. Basically, when "it matters", things get done quicker.
The difference is we know how to make the bridge, and knew where to place it. A lot of the effort in a new bridge is work that didn't have to be done for that bridge because it was already done. No need to figure out what to do with traffic (which means no phases that must complete first). No need to dig new footings, just use the old ones. No need to do a new design - the old one was good enough.
The bridge collapsed because of a fire and there seems to be no reason to redesign bridges to resist a fire like that so a lot of effort was saved. If we decided fires were too common we wouldn't be able to replace bridges as quickly because we need to do engineering work first on a new one.
We know a lot about making viral vaccines too so we have a lot of companies so a couple different methods get used and at least a few of them pan out. It's like if we could have 20 companies try to build the same bridge without interfering with each other and whichever worked became real.
People try way harder when the stakes are high, and everyone involved is at least a little terrified of being "the one who delayed it." That does wonders for cutting through pointless red tape and bureaucratic delays.
A minor example:
About ten years ago, a flash flood completely destroyed about thirty linear feet of the main road connecting the tourist district of Hershey, Pennsylvania to the rest of the town.
I assumed it would take weeks or months to repair, based on how long road work has usually taken in the area. It would have been a disaster for a lot of the local restaurants, economically.
IIRC, two days after the flood the road was back in order. It certainly didn't take more than a week.
Obviously, inventing a new vaccine is orders of magnitude more complex than fixing a road, but I think this aspect of human nature still applies.