Okay this may be far far away from actually being a thing, but if we break this down we can see its true value. Ok first off it's definitely worth mentioning that while Yoda was alive he trained two generations of the Skywalkers both Anakin and Luke Skywalker. Like the Skywalkers Yoda was very powerful but how powerful ? Enough that after he died he was able to be reborn ? Well lets see.
My theory goes like this, Yoda was seen as the perfect Jedi never once thought about turning to the dark side but what if in secret he became so powerful that he did not interfere only when his life was being threatened or when he must show his loyalty to the Republic, he fought against the Dark Side only so in the end he will reins supreme. A lot of people think Star Wars' Supreme Leader Snoke is Vader because how they look alike or that he is Darth Plagueis because he supposedly found a way to cheat death, there interesting theories but let stick with mine ok? Good so like i was saying Yoda trained both Anakin and Luke but favored Anakin more because he was so easy to manipulate and turn him to the dark side, but with Luke he was too much like his mother Pademe unable to see any benefit of going bad but he trained Luke to the point that Luke was able to redeem Vader and throw Darth Sidious of his pedal stool but still secretly annoyed at Luke for not opening up to the dark side.
And when Yoda died of old age he became a ghost Jedi still training Luke but plotting his rise to power, now 30 years later the First Order appear with Kylo Ren as it leader but what if Yoda or at this point reborn into General Snoke decided to get back at Luke where it hurts? His family. First he turned Ben Solo/Kylo Ren against Luke and ordered Ren to kill Luke`s apprentices forcing the veteran Jedi into exiled, but this was also his mistake because Luke could not be found Yoda or General Snoke could not track his process with the force and feared he could find another teacher and become so powerful that Luke could dethrone Yoda/ General Snoke as mentioned in episode 7. So now Yoda is focusing all his power on Kylo Ren training him up to fight and win against Luke Skywalker.
so why would everyone favorite green Jedi (apart from Kit Fisto) go from being the smallest bad ass to a freaking tall freak ? well that I don`t actually know I can only think because no one would ever questioned if Yoda was powerful enough to physically changed his body from a hobbit to a tall villain, or maybe he was tired of jokes thrown at him because of his height who knows? Anyway getting back this theory would explain through out the original trilogy and prequels Yoda was always concern about the Skywalkers and when he took General Snoke`s form he questioned Kylo Ren loyalties and how Luke Skywalker after 30 years would be a serious threat to him.
Thanks for reading hop you like it, be sure to check out my other posts. Love you all peace out