While Stoicism was indeed founded by Zeno[0] shortly after Alexander's death[1], the essential philosophy (Cynicism) was older, having been granted to Zeno by Crates, who had learned it from Diogenes[2].
Which is why we find in Epictetus[3]:
Furthermore, the Cynic ought to possess great natural charm and readiness of wit—otherwise he becomes mere snivel, and nothing else—so as to be able to meet readily and aptly whatever befalls; as Diogenes answered the man who said: "Are you the Diogenes who does not believe in the existence of the gods?" by saying, "And how can that be? You I regard as hated by the gods!" Or again, when Alexander stood over him as he was sleeping and said,
Sleeping the whole night through beseems not the giver of counsel,
he replied, still half asleep,
Who hath charge of the folk, and for many a thing must he watchful.
Which is why we find in Epictetus[3]:
Furthermore, the Cynic ought to possess great natural charm and readiness of wit—otherwise he becomes mere snivel, and nothing else—so as to be able to meet readily and aptly whatever befalls; as Diogenes answered the man who said: "Are you the Diogenes who does not believe in the existence of the gods?" by saying, "And how can that be? You I regard as hated by the gods!" Or again, when Alexander stood over him as he was sleeping and said,
Sleeping the whole night through beseems not the giver of counsel,
he replied, still half asleep,
Who hath charge of the folk, and for many a thing must he watchful.
[0] https://en.wikipedia.org/wiki/Stoicism
[1] https://en.wikipedia.org/wiki/Zeno_of_Citium
[2] https://en.wikipedia.org/wiki/Diogenes
[3] https://en.wikisource.org/wiki/Epictetus,_the_Discourses_as_...