Recent George soundbite where he says why Yoda talks that way.
"He was basically the philosopher of the movie, so he was talking about all the things. I had to figure out a way to get people to actually listen, especially 12 year olds.”
https://www.rollingstone.com/tv-movies/tv-movie-news/yoda-speak-george-lucas-explains-1235326334/
However, just a few years earlier Frank Oz said it was his own idea based on one line in the script:
“It’s funny you ask about that because I was just looking at the original script of The Empire Strikes Back the other day and there was a bit of that odd syntax in it, but also it had Yoda speaking very colloquially. So I said to George ‘Can I do the whole thing like this?’ And he said: ‘Sure!’ It just felt so right.”