Question from my kid: "How did Elvis Presley change music?"

My kid (8 years old) asked me how Elvis changed music, and I'm struggling to answer. I can think of popular songs he did, and examples of how popular he was. But that's not what my kid wants to know. My kid doesn't care about how popular Elvis was, or how much money he made, or records he sold, or what Elvis songs people still like. I've tried all of those answers, and my kid keeps asking "But why was he important?"

I think the question is something more like "How was music made after Elvis, that they didn't do before?" Which is getting to some kind of abstract point about music that's too technical for me to be able to answer.

Does anybody have an ELI6 to explain, how did Elvis change music? What was his enduring impact on music as a whole? How did Elvis change the landscape of music or directly influence other musicians?