I hope the origin of Snoke is discussed in some sort of flashback sequence that makes sense for the entire 9 movie series.
There are hints that Snoke is from the unexplored regions of the Outer Rim but my origin story is this:
At the time of his death, Snoke Ren was about 83 years old. Snoke is perhaps the last surviving victim of Order 66 as a former Jedi.
As a young, good looking man, vain and confident- Snoke was at best a moderately performing Jedi, relegated to more diplomatic and academic tasks than leading battalions in the Clone Wars. Thus he was low on Palpatine's priority hit list when Order 66 came down. He was attacked by clone troopers at docking port on Nar Shadaa but survived Order 66 thanks to random smugglers. Though badly maimed, worse was the trauma inflicted and the fear that grew inside him. After a limited recovery, he fled in fear to the unexplored regions after stealing a freighter. His fear instincts led him to kill the freighter crew, except the droids. That was the start of his journey into the dark side.
In the unexplored regions Snoke sought out survival and a way to destroy the sith. The only place he knew, from his days in the Jedi Temple Library, was the remains of the first Sith Temple. There he figured he could find a fundamental weakness in the Sith. A weakness that caused them to abandon this temple thousands of years prior. The dark side proved to be too tempting however, and he learned their powers, their ways. Despite this, he would not join the Sith. He would found his own dark society, one that did not follow the rule of two. Snoke figured he could have several apprentices, or a battalion, his own society in his image such as the Knights of Ren. After 26 years, he was a powerful master of the force at the time of the destruction of the second death star.
Years later he would find the leaderless First Order. After a demonstration of his incredible power and a convincing argument, officers quickly "bent the knee" to accept his leadership.
A few years later he would find the famous Jedi Master Luke Skywalker. He appeared to Luke as merely an old man, a surviving member of the old Jedi Order. "Was Master Yoda wrong?" thought Luke..."Was I not, the last of the jedi?"
He would tell his story to Luke but only to a point, he only stated he fled into the outer regions for safety. That he was too injured to participate in the rebellion. After befriending Luke, he gained access to Luke's students at the new Jedi Academy as a "guest lecturer" of sorts. This is when he first met Ben Solo.
What happened next, you can imagine. He corrupted young Solo before Luke could figure out what was going on. Once Luke did figure it out, he and Snoke fought in a private battle. He incurred more injuries but was rescued by the First Order, with a young Hux in the rescue party. Luke chased them in his X-Wing and owned a ton of legacy Tie Fighers/Intercepters. Nevertheless Snoke and Hux escaped to Hyperspace. When Snoke arrived at the capital planet of the First Order, a formal coronation took place, naming him as the Supreme Leader. Its worth noting, this title that reflects his respect for the military's position as primary institution in galactic rule. This public coronation, broadcast throughout the galaxy, revealed to Luke and Leia how deceived they truly were. To a young Solo, an inner conflict grew, out of admiration for the grandfather figure he knew. From this point on, they would converse across the Galaxy thru the Force.
