Little child's diary:
Why? Why? Why? Why?
Why? Why? Why? Why?
This is derived from the first line in the famous 2006 Jay Chou song Listen to Mom: Little child, do you have lots of question marks. It was nothing special till Tik Tok came along. Many video makers use this line as an equivalent of this , and brought memetic popularity to this line. Several derivative of this line are just as popular as the original meme, like the intentionally swapped version in artist commentary.
Basically, all a child does in this meme is bring up question marks--lots of it. Hence the visual joke.