Solution:
You are comparing two arrays: [Remarketing] == [Remarketing] while you should be comparing two strings Remarketing == Remarketing:
existentes[2][0]==cam[1][0]
Minimal Reproducible Example:
  const ar1 = ["Remarketing"];
  const ar2 = ["Remarketing"];
  console.log(ar1==ar2); // returns false
  console.log(ar1[0]==ar2[0]); // returns true
 
 
In case you had arrays with multiple elements you wanted to compare, then you can read this post on how to compare two arrays in JavaScript:
How to compare arrays in JavaScript?