There are millions of lines of code existent. There are thousands added. Your prior for it being Elon's addition should be something like 10,000/1,000,000 or roughly 1/100. The prior that it wasn't Elon's change is going to be something like 99/100.
When you add the additional information that Elon wants the code removed, but existing Twitter engineers think it appropriate to keep this actually increases the probability of it being added by the existing Twitter engineers and decreases the probability it was added due to Elon.
Obviously, these are rough numbers, but hopefully seeing any numbers at all helps you to get an intuition for the math.
