10 Star Wars Theories That Make Appalling Sense
4. Yoda Is A Sith
A deeper cut on Yoda is that the diminutive Jedi guru was a Sith all along. Yoda is the thread that ties the whole Star Wars saga together. He's present from the beginning of the prequels to his shuffling off the mortal coil in Return of the Jedi. Only The Force Awakens and Rogue One are lacking his pointy-eared presence, and his influence is felt throughout the whole series.
This theory posits that as a Sith, Yoda has been manipulating events to first destroy the Republic and Jedi Order by allowing Palpatine to seize power as the Emperor (note how Yoda made sure he survived the Jedi purge after Order 66), and then trained Luke Skywalker to destroy Palpatine and his apprentice, Vader.
That puts Yoda as the halfway point of his plan to rebuild the whole Republic and the Jedi from scratch. Now he pursues his plan as a Force Ghost (and possibly in holographic form as Supreme Leader Snoke) to both bring the new Republic to its knees, and destroy everything Luke Skywalker loves.
Yoda's ultimate end game is for a desperate, broken Luke to fall to the Dark Side and become the Republic's new dictator, utterly in Yoda's thrall as Palpatine never was.