December 2, 2001 – Enron files for bankruptcy
February 19, 2004 – Jeffrey Skilling surrenders to the FBI, released on $5 million bond
January 30, 2006 – Trial starts
May 25, 2006 – Jury returns verdict
October 23, 2006 – Skilling sentenced
December 13, 2006 – Request to remain free during appeal denied, prison sentence begins
Enrons crimes were more legally dubious because they had followed accounting rules in a convoluted way. The end result wasn't legal, but the individual steps in isolation were arguable. So prosecutors had a daunting task. FTX seems to have flagrantly flaunted not just laws but even basic accounting.
Enron was a big hierarchy. Kind of like a mob trial, they got each lower level to turn on the next level. They had to prove the employees doing the actions weren't just rogues. Here, it's straight to SBF.
Skilling was smart enough to hide behind a lawyer and deny everything. SBF seems to be admitting to various aspects of the crime in conversations with journalists.
An added wrinkle is the Bahamas and the US (at least) want to try him. It might take time to figure out which tried him first. But I expect that's a fairly quick process.
In one Twitter interview he seems to argue that his company did the same thing you describe about Enron: Steps that seemed fine in isolation but got out of hand.
But the details look different. He admits that FTX said they never invest the deposits. He then claims he loaned that money to Alameda who invested the deposits. That seems like an important pair of details. Those two things help combine with other facts to build the legal case. He also admits he didn't really lend them out to Alameda, probably because it evaded the margin limits.
Look, he's not running around saying "I ran a giant fraud". He may even think he did nothing wrong. But he is agreeing to some of the pieces prosecutors need to prove. Given FTX's bad records, just confirming basic facts is good for the prosecution.