Confusion with .copy() and .remove()

I'm having some trouble understanding why looping over a copy of a list doesn't have the same result as looping over the original list. There have been other questions similar to mine and great answers, but I am still having issues understanding.

Let's say:

letters = ["a", "b", "c", "d", "e"]
for letter in letters:
    letters.remove(letter)
    print(letters)
#output is ['b', 'd']

I get that the above is because when we start, the indexes are a = 0, b = 1, c = 2, d = 3, and e = 4 and then after we loop once, the indexes are shifted to b = 0, c = 1, d = 2, and e = 3, and so on and so forth each time we loop. And for every loop, the computer goes on to the next index to remove (loop 1 removes [0], loop 2 removes [1] - which is now c - and so on).

So, when we change the code to this

letters = ["a", "b", "c", "d", "e"]
letters_copy = letters.copy()
for letter in letters_copy:
    letters.remove(letter)
    print(letters)
#output is []

Why does this not do the same thing as above? We are looping over the copy of the letters, so doesn't the computer do the same thing: loop 1 removes [0], loop 2 removes [1], and so on to the original list since we are removing the letters from the original list? (After removing a, b is now [0], and since the loop is running again, why doesn't the computer move on to [1] since it just did [0] with the original list, therefore creating the same problem as before?)

Thank you in advance! Let me know if anything I asked is confusing!