People who work in the field for a long time tend to have a certain bias towards a solution. Often these people are stuck in a local maxima. Outsiders can offer a new perspective that results in a breakthrough, usually by starting from first principles or looking at different side-tracks that used to lead to a dead end.
A great example is Musk's SpaceX: when he noticed how much he had to pay for a rocket engine, he went back to first principles and said: "I'll just build it myself". Combine that with the insight that a rocket should be able to land properly to make re-use a valid option, and it disrupts a whole field.
And once someone did it, others know it's possible and start achieving it as well.
Sometimes ignorance is bliss. Just think about George "Good Will Hunting" Dantzig [1] with the (in)famous "I assumed these were homework assignments, not unsolved math problems" [1] or Eliud Kipchoge running a marathon in under 2 hours.
"I can't understand why people are frightened of new ideas. I'm frightened of the old ones."
- John Cage
High hopes!
[1] https://bigthink.com/high-culture/george-dantzig-real-will-h...
