You can slice and dice the success of Tesla and SpaceX in all sorts of ways: analyze the external factors, the market, their employee compensation stratagies, the competitive environment, and so on, and you will probably find several interesting factors which were a contributor to their success.

But to ignore the visionary leadership and determination of Musk as a core factor to this success on the basis of other "motivated" entrepreneurs failing would be, I think, unwise. One of the defining charateristics of many of the leaders who have shaped our present is that they are/were resolute in some belief, even in the face of setbacks. Others with firm determination having failed isn't an antithesis - I'm not claiming this represents the only factor for success in business, but rather that in the case of Tesla and SpaceX this attitude that achieving their lofty goals was possibe, was a core driver in theirs.

Edit: BB typo