And McCabe and Bokonon were just the last in a long, long, long line of colonizers that came to the island.
Hernando Cortes first conquered the island for Spain and Charles V in 1519.
They found nothing of value other than a few natives to burn for heresy and giggles. Awesome.
After the Spanish, San Lorenzo was taken over by—deep breath—the French, the Dutch, the Danes, the English, and some freed slaves.
The last group formed an empire underneath the Emperor Tum-bumwa. Tum-bumwa built fortifications on the island to protect his empire, but since no one in their right mind would fight for San Lorenzo, they remained unscathed.
After that came the Castle Sugar company.
When McCabe and Bokonon came in 1922 and said they were taking the island from the company, the company just walked away.