he wasn't the first emperor to seek out or succeed at finding a way to be immortal

Darth Vitiate who ruled over the old sith empire extended his lifespan by consuming the life forces of every living thing on 2 planets...along with many of his enemies and rivals

Darth Andeddu, who ruled over a whole planet figured out how to transfer his spirit to another body. That method is very risky...a lot of dark jedi and sith succeeded at the leaving their own bodies as ghosts, but failed at the second part at various stages of the process. There were some that failed because the person they took over was too strong willed to be taken over and others failed because the people they tried to take over weren't force sensitive

Then there's Darth Plagueis who succeeded at manipulating the force into constantly refreshing dying cells in his body to be completely self sustaining with his everlasting life.

When i read the first sentence of your comment i thought you were talking about the real-life emperor and i got very confused for a second there lol.

hey man...it happens