ok you asked for it, here's my version of Watcher/Listener Lore 101 (contains evo spoilers if you don't want those):
evo smp was in fact the originating point of the watchers. as you'll have seen, the watchers were originally conceptualized by grian as a way to give a story element to the updates; they were the ones responsible for creating the update portals, and they would leave riddles and clues guiding the players towards them. and as you'll see, they weren't so much direct villains as they were simply capricious godlike figures seemingly with their own agendas.
however, something else you'll see throughout evo is that the watchers could be very harshly and arbitrarily punishing towards the players for breaking certain "rules"; examples include the time they put obsidian over all of grian's chests as punishment for his greed, or the time they destroyed the property police's base with a meteor for taking taurtis's vacant seat as mayor.
fast forward to the end of grian's series: after finally reaching the update that introduced the end, the evo gang all teamed up to beat the dragon, only when they hop through the portal instead of all going to the same end, they're separated and each have to face the dragon on their own. after beating the dragon and going through the portal, the watchers speak to everyone through a modified end poem in which they reminisce about the memories the players made on the server, and then basically say "btw we're taking grian and he's becoming one of us". at the end of this dialogue, grian joins the two voices and bids farewell to the evolutionists, saying that he's sad to go but looks forward to watching what they'll do. hence, we get Watcher Grian.
(a note on this: grian revealed later, when he was a guest on pixlriffs and joel duggan's podcast The Spawn Chunks, that the "watchers" were meant to be like a metaphor/allegory for the audience, i.e. the actual watchers of the series. they were arbitrarily punishing because audience comments could be extremely harsh when ccs didn't follow expectations, and they took grian at the end because he was ending his series, and thus would become a watcher as opposed to a player on the server.)
as for the origin of the listeners: they were a force similar to the watchers, but i believe they only really interacted directly with martyn and jimmy. i'm a little rusty on the timeline as it's been a while and i haven't watched either of their evo series in full, but iirc the listeners first cropped up not terribly long before the dragon fight. martyn and jimmy discovered a mysterious symbol and messages containing the phrase "there are those who watch. we are those who listen." and basically the listeners told them to wait for further instructions.
after the dragon fight, the evolutionists minus grian were sent back to the overworld, but found themselves thousands of blocks from spawn. they were essentially told by the watchers that they had to start completely fresh with a new spawn; they could bring some of their old stuff, but only whatever they could carry on them.
however, jimmy was for some reason NOT sent to this new spawn, and instead was left back at the old spawn where all of the buildings they'd made there were broken down and decaying. jimmy, alone at the old spawn, found a message from the listeners, who expressed that they found the watchers' decree too harsh, and wanted to help the evolutionists by giving all the players ender chests, allowing them to almost double their carrying capacity. thus we get this impression that the listeners are opposed to the watchers, and are more merciful towards the players.
after that, there's not a whole lot else from canon. evo as a series sorta fizzled out over time rather than coming to a firm conclusion. thus, the rest of the watcher/listener lore comes from either fanon, or from martyn's life series/vtuber lore. WHICH I WILL CONTINUE ON IN A SECOND ASK.