I don't know where you got the information that Elon Musk was behind Shiba, but I think it's just rumors.
Yes, it may be just rumors, I do not know explicitly if he had anything to do with Shiba, but the talk on social media was that Elon Musk bought large quantities of Shiba because he tweeted a picture of his puppy (the Shiba breed) on Twitter, but Elon Musk denied that he owned Sheba.
The ones that bought those meme coins will try to use every single detail to try to make their coins pump, even if at the end that information is proven to be false, as what matters is not the legitimacy of the information being shared but the possible reaction they can create and the pump the meme coin can experiment, in a way meme coins have their own rules when it comes to what can affect their price, and only those which are willing to invest in those coins know how to take advantage of those rules.