The lack of flash-to-bang time for a start. I'm no scientist but that speaks volumns.
I think it has been previously covered on here, however - in this, unlike other vaccines, they threw the kitchen sink at it.
There is little profit in vaccines - okay they make millions, but as a percentage of profits it is tiny. And why spend billions to make a few millions profit from vaccines when you can splash out a few million for a new antacid that will rake in billions.
In this the government and charitable institutions threw research money at the firms.
All the ethical, lab and financial committees were told to answer their emails NOW and not meet up every 3 months to consider making a decision at the next meeting.
Labs, funding, computers, analysts, lab techs etc were all made available - as were lab animals.
Volunteers came forward in their 10’s of thousands - normally in trials you struggle for years to fulfil the required cohort numbers but in the US they got 140,000 (IIRC) almost immediately.
And because the disease was so prevalent the placebo cohort got the required number of infections needed to demonstrate efficacy in a very short time.
What people should be screaming about is why does it take so long to create a vaccine for kids being born with funny looking heads in the third world when we can knock one out in months when old white men are going to die instead?
All of this is available open source by the way, this explains some of it quite well.