Mao kinda sounds like "meow" (for English speakers at least) so I believe that's why there are some memes like this that portray him as a cat.
I don't know a whole lot about the meme itself, but the idea that Winnie the Pooh is banned in China is just made up and has no basis in reality. Xi has better things to do than ban cartoon characters that western libs associate him with.
By the way, good on you for asking questions and trying to learn. Please don't be ashamed or afraid of asking questions, people here are very kind and friendly!