It's like quitting smoking. If you're very good at quitting smoking, because you already quit 6 times, it means the first 5 times you haven't really quite. If Rome fell 6 times it also means at least 5 times it didn't fall for good and thus it took more than a day to fall for good.
If you want to make the case that Rome did not fall in a day, that's fine, you may have even made the case in your comment. I was just commenting on using the stock phrase wrong and expecting it to resonate.
For example, I can say "An apple a day sends you straight to the doctor." If I said that, most people would recognize that I had twisted the original phrase, and could decide if they wanted to engage with what I wrote. But if I wrote, "just like an apple a day, gluten every day will send you to the doctor", I'd expect more pushback from people, "hey, wait a minute, that doesn't make sense"
