This statement assumes that there's such a thing as free will and original thought. I know that this is a completely different, philosophical and metaphysical discussion, but still fundamental to the question of "how to be successful?"
No no, the second part of the statement, "the courage of their convictions", that is the rare part.
New ideas are common and most are just laying around in the ether to be picked up or put down at ones leisure. Only novices or fools think they're the first person to pick up a given lane of reason.
Its only the true imbeciles who decide to jump off a cliff and risk it all on an internal belief that they've 'got it right' with whatever they're doing that make it. There are plenty of cowards with ideas who never make it. Those aren't the people we're talking about.
The demonstrative proof is that everyone is free to take an idea and try and fly with it by jumping off a cliff. The rarity is that almost no one does it. The selection bias is that we only acknowledge those who do fly and not the pile of bodies at the bottom of the cliff.
For practical purposes, it’s best not to worry about determinism so much, and adopt the belief of compatibilism [1], which many institutions in society—such as the courts and legislature in Western countries—effective assume (if not free will).
The existence of original thought also matters less than the ability to effectively execute a plan to create a useful good or service, for the purpose of career development.
[0] Stanford Encyclopedia of Philosophy: https://plato.stanford.edu/entries/determinism-causal/
Any `how to` discussion presumes free will as a fundamental axiom.
Note that I don't believe any of this to be true, but it's an interesting thought experiment.