The following contains spoilers for Jurassic World Dominion, now in theaters.
Since Jurassic Park III, audiences haven't returned to Site B, Isla Sorna. The island that served as the staging ground for the dinosaurs before they reached Jurassic Park got restricted ever since the events of The Lost World: Jurassic Park. As a result, when people were trapped, many buildings had fallen into disrepair and were overrun by dinosaurs. But now, thanks to Jurassic World Dominion, the answer as to why has finally been fleshed out.
Since these islands existed in the pacific, they were prone to constant hurricanes and other severe weather. In The Lost World: Jurassic Park, John Hammond explained that Isla Sorna had been "wiped out" due to Hurricane Clarissa, which caused everyone to evacuate. However, an evacuation was clearly only the simple answer as a short video during Jurassic World Dominion from Charlotte Lockwood, the areas were abandoned following the hurricane. But in doing so, it showed just how careless the scientists were at the time and remained nearly thirty years later.
It's clear that the severity of Hurricane Clarissa put the humans and buildings on Isla Sorna at great risk. Because of this, their leaving of the property made perfect sense. Even if they had to close the facility entirely, freeing the dinosaurs was also a responsible choice. That said, issues still have yet to be addressed. For starters, the rate the site got abandoned seemed highly suspect, as if they wanted to clear up any possible evidence of their actions, considering no one but Hammond and those at InGen were made aware of the location until after the events of The Lost World.
This choice also fits more in line with the book's reasoning for why the island got abandoned because InGen went bankrupt. While the company wasn't financially incapable of functioning at the time, the way they cleared out and left everything without intention to return proved that, at the very least, they treated the site and its assets as property rather than responsibility. That continued long after they left the island as they also tried to capture some dinosaurs for their attempt at a park in San Diego.
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Remorseful of his choices that led to the accident at Jurassic Park, Hammond eventually decided to continue studying the dinosaurs and protecting them from the likes of InGen. That further got bolstered by the dinosaurs overcoming the lysine contingency meant to kill them. However, despite Hammond trying to make up for his past, it proved futile because the action on Isla Sorna had grown far beyond the hurricane and its abandonment.
Jurassic World Dominion was about bringing things full circle and showing audiences that some lessons aren't learned even over decades. While Jurassic Park seemed like the first lesson, the continued work after the incident proved that only an act of nature could stop an equally destructive attempt to play god. Isla Sorna has since gotten protected as one of the few safe havens left for dinosaurs. However, it's also proof that even after Jurassic World Dominion, and the light it shed on the event, it's just another example of how humanity can't stop meddling in things they don't understand.