Site B, officially named Isla Sorna, was where the majority of both The Lost World: Jurassic Park and Jurassic Park III took place.
All were abandoned on Site B, until the surviving animals were reportedly moved to Nublar to be housed as future attractions at Jurassic World.
Isla Nublar was totally wiped out during the events of Jurassic World: Fallen Kingdom.
Basically, Masrani Global, the company that took over following John Hammond’s death, went into a freefall after Simon Masrani’s death and the incident at Jurassic World.