That's not true at all.
The oil rig is/was owned by the former chief minister of Sabah who hails from Labuan island who had planned to open a casino off the coast of Sabah next to Labuan. But the permit to open a casino was rejected by the federal government despite several attempts to get the permit and it dragged on for some time.
Someone suggested to him to convert it to a diving center instead and to park it off Mabul as Sipadan was gaining prominance at the time globally due to word of mouth and internet advertising/blogs and articles and instead of investing in building a resort at the time on Mabul (and buying land), he simply got approval from the state government to park the rig off mabul in safe waters (shallow waters) on top of an atoll.
His daughter in law now runs the business and has been doing so since the inception of seaventures.
He tried also getting a casino license thru the sabah government but because of personal disputes with the then chief minister, that too was flatly turned down...