JavaScript Not Running/Displaying

Weird, sounds like a Replit issue TBH.
Also, I wouldn’t rely on AI.

Also also, why are you using snake_case?

Also also also, why are you using both let and var?
Here’s a tip: Whenever you’re making a variable with document.getElementById, use const because that variable will likely never change.
For everything else, use let.

Also, .onclick isn’t recommended.

const btn = document.getElementById("submit");

btn.addEventListener('click', event => {
  event.preventDefault()
  ...
});