Complex sentence: Much of Culburra Beach's land was bought by Henry F. Halloran who thought that Culburra was going to be Canberra, But his plan backfired and had a lot of land and not much to do with it.
Split into simpler sentences: Much of Culburra Beach's land was bought by Henry F. Halloran who thought that Culburra was going to be Canberra. His plan backfired and he had a lot of land and not much to do with it.