Pythagoras discovered Mathematics and MusicHe most certainly did not. Both were well known long before he was born. He (or members of his school) made some discoveries that relate mathematics to music.
The ancient Stoics developed a protocol for the life of a pious person, which is absolutely relevant to this day.
Stoicism has become a popular meme lately, but it bears only a faint resemblance to the Roman version of Stoicism and even less to the Greeks arguing in the stoa. Their philosophy is worth studying, but no more so than anything else in the vast sweep of philosophical history.
Euclid collected knowledge in one book
Knowledge about geometry, an important field but hardly a complete book of knowledge.
Eratosthenes calculated the circumference of the Earth with an accuracy that was surpassed only in the space age
This is true, but it hardly seems to justify that they were "much better people than we are". Eratosthenes had an extraordinary tool at his disposal: a class of soldiers specifically for measuring distances by walking them. He was hardly the only one to have the basic idea of using triangulation to calculate the size of the earth. He also had the best raw data.
I don't mean to demean them or your interest in them, but they were just men (and occasionally women). They were neither better nor worse than us; they are us.
Aristotle was a scholar of extraordinary breadth and extraordinary depth. For centuries he was venerated more than was really merited, and most non-philosophers today who know anything at all about him remember him mostly for his real howlers. But he did systematize knowledge in a way that eventually helped lead to the notion of science as we know it today.
Philosophy too often proceeds by treating individuals as if they produced scripture. That frustrates scientists, who rarely read anything in the original and would certainly never declare that you didn't understand something if you couldn't read the primary source.
Philosophy has more akin to literature than to science, where the specific writing matters. "Natural philosophy" was the least like that and broke off into a separate field we call science, and in its rush to stop venerating individuals often forgets history -- and then mangles it.
Which is to say... if these specific writers mean something to you, that is fantastic. Though for the writers you mention, most have left only fragmentary works, and the actual attribution of them to specific people is doubtful.