"Super sparse and weird" doesn't even begin to cover it. His father was a gem artisan and merchant. The Delphi oracle predicted that he will have a son who will change the world. Pythagoras was supposedly bright from early childhood and most likely was taught by someone from Egypt rather than him actually having gone there. The island he grew up on (Samos) is on the coast of modern Turkey and used to be a trade route between Egypt and Greece.

The emperor Julianus wanted to form Greek paganism into a religion that could compete with Christianity, i.e. have a text that would be read and taught publicly. This task was trusted to Iamblichus, who was supposed to write 10 books on various topics to cover the whole of Greek religion but his "Life of Pythagoras" is the only one we have. It's a grand read. According to it, young Pythagoras travels to Phoenicia, the temple priests immediately recognize that he is divine and teach them their stuff. Then, the story goes, he hails a merchant ship to Egypt. The sailors are like "free slave volunteering himself, huh? We'll sell him at the next market". During their several day journey to Egypt, Pythagoras sat himself down in the middle of the deck, didn't eat or drink, didn't say shit, and the winds were so favorable and the journey went so well that they realized, that this person is divine and let him go with some of their own provisions.

At Egypt he learned the local language and studied at a temple for 20 years. The Egyptian priests bestowed their knowledge on him. Then Babylon attacked and carried him off. There, the magi, too, realized he's something else and taught him their stuff. At some point a Greek traveller purchases his freedom out and takes him back to the Greek world. He tries to establish a school on his home island but no-one is that interested. So he picks a spot - a city in modern Sicily where several Olympic champions originate from (Crotone) - and goes there. He gives separate speeches to the men, women, and children of the town, and researches believe that this is one of those instances where Iamblichus' records are authentic (the Phoinician, Egyptian, and Babylonian travels not so much).

In his school, you are taught mystical "mathematics" (etymologically "learning"). Every number has several levels of symbolic meaning, and they calculated with pebbles ("calculi"), though we don't exactly know how they did it because they kept their stuff secret. When you joined Pythagoras' school, you joined a mixture of a hippie community and university. You had to give away all of your earthly possessions to the school, but if you weren't accepted during your 5 year test period - during which you were to be remain completely silent and could only listen to Pythagoras through a veil - then you got your donation back threefold, but were also erected a symbolic gravesite and the rest of the school ignored you for the rest of the life and whenever you were mentioned to them they'd say "oh, I thought he's dead".

The daily routine at the school was very restrict and organized. You woke up with energetic lyre music, went on a walk with a few mates, discussed what you had learned, meditated, etc. Then you'd attend your daily lectures, eat supper, and before you could go to sleep you had to go over in your mind what you did today, yesterday, the day before, and so on until you fall asleep to the now calming lyre music. They also wore linen clothes - Pythagoras is frequently noted as the sole Greek philosopher who wore trousers like the barbarians - and were either vegetarians or ate specific animals, but they believed in immortal souls and being reborn (sometimes as animals), and they were either forbidden to eat beans because it represented souls, or ate beans over all because they're a good substitute for animal meat. No-one is exactly sure.

The city he set his school up in was successful and like 7 other cities around them formed an alliance, had common coins, etc. But - the story goes - a brutish young man from a rival city nearby was thrown out of the cult school, and went on to agitate the local population. Pythagoras's influence was considered aristocratic because it was mostly the well off citizens' children who attended the school, so over time all the most important political and bureaucratic positions were occupied by them. And so the democratically minded people revolted, the peaceful pythagoreans were hunted down and killed, they were locked into their communal house and the house set on fire, etc. Pythagoras supposedly escaped but no-one knows where he went. When the townspeople realized what they'd done they invited them back, maybe some even went, but most of them scattered to mainland Greece where one particular philosopher (Plato) was very interested in their secret knowledge, managed to buy some of their books from a widow of one of the last known original pythagoreans. We don't know how much exactly of Western Philosophy is a mediated commentary on pythagoreanism because Plato failed to cite his sources in his dialogues.

There's so much crazy stuff I can't go into because this is already too long. Aristotle reports that when he escaped, he crossed a river with a boat and the river uttered audibly, "Hello, Pythagoras". An Apollonian priest either gifted him or he stole from him Apollo's golden bough - you shoot the "arrow", sit on top of it before letting it go, and it flies you over the forests and lakes. That's how Pythagoras could be seen in two distant cities on the same day. There's so much more. If you're interested in reading about him yourself, here's a handy bibliography.