Why did Napoleon’s return to power not last?

Beacuse when his enemies heard Napoleon had returned, they had declared him an outlaw and sent troops to defeat him, and defeated him at the battle of Waterloo.
i hope it helps!

Because a massive European coalition of i believe Prussia Russia Austria Sweden and Britain crushed him and he didn’t make it any better by going on the offensive that why it’s called the 100 days war it did not last long for Napoleon however if he had gone on the defensive and maybe used gorilla warfare he could have lasted longer and been a real trouble for the coalition.