So, if they collected their taxes and grew their wealth over time, then they could create a empire. We all know that they are affiliated with powerful bounty hunters, and have an iron grasps on Nal Hutta, and then Jabba finds another poor planet, and become a crime lord there, making his wealth even greater.

Why are the Hutts so strong?

The Hutt armies enslaved those species they deemed useful and exterminated the rest, eventually establishing a Hutt empire that was for two centuries the most powerful galactic government in its time. The more worlds they ruled, the more wealth filled their pockets.

Are Hutts immune to the force?

Much like the Toydarian junk dealer Watto, the Hutts are among a handful of exceptions in the galaxy who are unaffected by the Force's mental influence. Originally introduced in Return of the Jedi, when audiences initially encountered Jabba the Hutt, it was revealed that the gangster is impervious to Jedi mind tricks.