That's true, though I would guess that for the upper echelon success you need all: luck, timing, intelligence, competence, etc.

"Syndrome" just means this is a common pattern for successful people (independent of whether they are right or not about the role of external factors to their success).

For example, from the article about entrepreneurs and impostor syndrome (linked from the Wikipedia entry):

"Psychological research done in the early 1980s estimated that two out of five successful people consider themselves frauds".

http://www.inc.com/magazine/20060901/handson-leadership.html