Yoda and the High Council did not know about Order 66, but they did know something was wrong with the clones. During a battle in the Outer Rim, a clone trooper named Tup had a mental breakdown mid-battle and killed one of the Jedi generals leading the battle.
Did Yoda know the Jedi would fall? According to TCW Season 6, he did, to some capacity, he didin't know exactly when, why, or who was Sidious, but he did know all the Jedi were going to die, and he also knew the Clones were set up by the Sith.
So, it's likely Yoda didn't want to interfere and alter the future, as he'd be at risk of preventing the Sith from being defeated many years later. While Yoda sensed that the Sith's plan involved the Clones, it was too late to prevent Order 66.
And even if he were to win, there was no guarantee that the new Empire would come to an end. So, by accepting the loss and hiding away, Yoda knew there was hope for new Jedi, ones who could learn from his mistakes and defeat the Sith once and for all.
Star Wars Confirms Yoda Turned to the Dark Side - and Almost Became the Most Powerful Sith Lord. With the aid of Count Dooku, Yoda could have potentially destroyed the universe if he had gone to the dark side in Star Wars.
Although his choice to help with the droid attack on the Wookiees seemed to be a prudent one in Star Wars: Episode III - Revenge of the Sith, Yoda's Kashyyyk mission was actually his worst mistake.
Why didn't Yoda want Obi-Wan to train Anakin? Lines spoken by Yoda to Obi-Wan in The Phantom Menace. Yoda accepted the possibility that Anakin might be the Chosen One, but he still feared that training him would be dangerous, and was against his being accepted into the Order.
Unfortunately for the galaxy, as Palpatine grew in power the shroud of the dark side fell over the galaxy, diminishing the Jedi's ability to sense the Force. Thus Yoda failed to realize how close to home the Sith really were - until it was far too late.
Yoda ultimately managed to dislodge Sidious's lightsaber out of his grip, disarming him. Sidious eventually took the high ground by jumping to one of the Senate pods above him.
Reva Sevander is introduced in 'Obi-Wan Kenobi' and is revealed as a youngling who survived the Great Jedi Purge. Reva survived Anakin Skywalker's massacre at the Jedi temple on Coruscant by playing dead between the bodies of her fellow younglings and friends.
R2-D2 is the candidate most suggested when theorizing who could have saved Grogu. R2-D2 was on Coruscant during Order 66. While it did not show the droid during the initial march to the Jedi Temple, he was clearly seen in Anakin Skywalker's starfighter when he visited Padme after the massacre.
Before she became a Jedi hunter, she had possession of a droid. However, it was taken away from her, like many of her past belongings and acquaintances. During her time as an Inquisitor, the Third Sister wore black armor with a cape, and wielded a red-bladed Inquisitor lightsaber.
Over the years, Anakin came to highly respect Yoda, while Yoda gradually outgrew his fear of Anakin and came to have faith in him and correctly came to believe that Anakin was the Chosen One from the Jedi prophecy.
Yoda held the title of Grand Master of the Jedi Order since the days of the High Republic Era. At some point, Yoda took on a human named Kantam Sy as his Padawan. The two were stationed at the Jedi Temple on the planet Endovar.
While the Shaman of the Whills was not there to carry on his teachings, Qui-Gon was able to pass on his knowledge of immortality to Master Yoda. He instructed Yoda to meet with the five Force Priestesses: Serenity, Joy, Anger, Confusion, and Sadness.
Palpatine admits to Darth Vader that the Jedi he actually feared most was none other than Jocasta Nu.
In Darth Vader: Dark Lord of the Sith #7 by Charles Soule and Giuseppe Camuncoli, Emperor Palpatine admitted that the Jedi he most feared was not a skilled fighter or a Force prodigy, but a relatively weak Jedi.
In The Rise of Skywalker's novelization, written by Rae Carson, it's revealed that Rey's father is a failed Palpatine clone. He was initially created as a vessel to house the Sith Lord but proved incapable of doing so.
Anakin Skywalker, the Chosen One, possessed the highest known count in galactic history—over twenty-thousand midi-chlorians—surpassing the potential of Grand Master Yoda and all Jedi.
Obi-Wan's Early Years
“I was identified as Force-sensitive and taken to the Jedi Temple on Coruscant.” In Marvel's Obi-Wan comic, we get a glimpse at his childhood there as a youngling. He began training under Master Yoda as a youngling until Qui-Gon Jinn chose him as an apprentice when he was 13 years old.
Yoda allowed Obi-wan Kenobi to train Anakin Skywalker because Obi-wan was clearly bound and determined to follow his late Master's dying wish. Obi-wan was going to do it either way, and at least this way Yoda and the other Masters would be able to counsel the headstrong young Knight if he got into trouble.
When Obi-Wan tells Yoda that Luke is their “last hope,” Yoda says, “No. There is another.” While the events of Return of the Jedi suggest this “other” person was Leia, it's also possible Yoda was referring to Rey.
Legend had it that Yoda—a Jedi who became Grand Master—was trained by N'Kata Del Gormo. A Force-sensitive Hysalrian, N'Kata Del Gormo was trained in the ways of the Force and achieved the rank of Master within the Jedi Order.
Yoda : [Deleted Scene - A dying Yoda confesses to Luke about the truth about Darth Vader] Unfortunate that you must rush to face him. And in complete of your training. That no ready the burden with you.