Perhaps these are the "best thinkers that the world has ever seen" because they said stuff that was beneficial for (some) powers that be. E.g. Plato-Aristotle-line/myth is directly linked to Alexander the Great.

Worth noting that there were very influential thinkers and entire schools of thought that looked beyond their noses. A good example are cynics/Diogenes the Dog, who may well have been more influential than the Platonic line. E.g. (as per anecdotes we have left) Alexander the Great had great respect to Diogenes, who totally ridiculed Alexander's (and Plato's) position.

Also stoics (e.g. Marcus Aurelius) are quite direct descendants of cynics and not ashamed of this at all.

More I look into classical philosophy, or the "myth" of academia, more it seems that it's mostly a fabrication of perhaps scholastics.