Cato Neimoidia was one of the earliest Neimoidian colonies. The planet itself wasn't worht much, but the Neimoidians needed a good place to store all their expensive stuff. During the Clone Wars, the Neimodians obviously wanted to protect the planet, and it became one of the most heavily fortified planets in the CIS. That just provoked the Republic all the more. Many lives on both sides were lost in the Battle Of Cato Neimoidia so that the Republic could capture some fancy furniture and piles of devalued currency. As part of Order 66, Jedi Master Plo Koon was killed by his own Clone Pilots.
Only the wealthiest Neimoidians were allowed to live on Cato Neimoidia. Even so, they mostly just keep their junk there and live elsewhere.