Here's a hypothesis: When Hutts first emerged as an intelligent species, they were symbiotes with some other large creature, like remoras with sharks. The Hutts supplied the "brains" to the "brawn" of their partner-creatures, and it is these creatures which provided the muscle power for their civilization until the Hutts discovered fossils fuels, nuclear power, and other innovations which made muscle obsolete.

Perhaps, after contact with interstellar civilizations, the Hutts either did not carry their partner-species into space due to the life support requirements, and instead adapted into 'symbiotic' relationships with the other spacefaring peoples. They provide brains and expertise which allows them to act both as politicians or as crime lords. In Jabba's case, the relationship is more "parasitic" then symbiote.

Yeah, it's probably not backed up by anything at all in canon but I think we've got at least the bare bones of a plausible tale here.

Respectfully,

Brian P.