This is a simple one: allow people to change their mind when they have found new information supporting the change.
I'm not talking about people who change positions all the time. I'm talking about skilled people you are working with who need to make fast decisions all the time. It is really empowering if you actually give them the right to change their mind, if they have found valid data to back them up.
If they feel safe to do so, without getting chewed out for “missing this particular point in the first place”, you're on track to start moving faster. If you don't, people will block off more and more time to do their research and this in turn will block everyone who is waiting on them to make a decision.