Gillgan was the original control agent and the castaways were being used as guinea pigs for what would later develop into "Project Lost". Both were experiments devised to learn how one might control people from different walks of life by putting various manufactured pressures on them.

Was Giiligan really that stupid, stupid enough to foil so many attempts at rescue/eascape? I don't think so... He was a genius, purely and simply a devious diabolical genius.

He briefly allowed the castaways to be "rescued" only to return them all to the island so he could observe whether or not a robot army he was tinkering with would be sufficient enough to take over the world quickly by force if the outcome of his experiments weren't satisfactory.

Yes, the Harlem Globetrotters saved the rest of us from enslavement by Gilligan and his robots...

When it was determined that the "Castaway Project" was a failure and that an occupational force would not work he knew what must be done. Though the Castaways had their differences, they essentially could work with one another to make coconut cream pies and washing machines.

This was easily remedied for "Project Lost".

Errrr... Ummmm... Nevermind. LOL