Yoda went into exile rather than continuing to fight
Yoda is the most powerful Jedi who ever lived. Despite all this, instead of joining the uprising Rebellion, he went into exile on Dagobah. Some of this was for his own protection, but a lot it had to be based in fear. Yoda was certainly aware and scared of Order 66. He knew that if he showed his face in public, he would be hunted down. Yoda should’ve been strong enough to first sense any attacks coming, and then fight them off if they did get too close. Instead, he just hid.
Yoda also was pouting for losing his fight with Sidious. He battled to a standoff with the most powerful and evil Sith Lord to ever live and as soon as he lost, he declared that he must go into exile. That seems like a chicken move for a powerful leader of a powerful group but that is what Yoda chose to do.
If Yoda was a strong leader, he never would’ve given up the fight. Sure he could’ve hid for a few years, but then could’ve sent his buddy Bail Organa a signal to come and pick him up. The Rebels could’ve benefited greatly from having Yoda in their corner, and wouldn’t have had to let the galaxy suffer for years under the oppression of the Empire if Yoda would’ve joined the fight.