"I also worked in these halls through the genocides against the Tutsis, Bosnian Muslims, the Yazidi, and the Rohingya. In each case, when the dust settled on the horrors that had been perpetrated against defenseless civilian populations, it became painfully clear that we had failed in our duty to meet the imperatives of prevention of mass atrocities, of protection of the vulnerable, and of accountability for perpetrators. And so it has been with successive waves of murder and persecution against the Palestinians throughout the entire life of the U.N.," he continued. "High commissioner, we are failing again."

When Western Governments say "never again" after horrific genocides, what they really mean "We won't let these happens when our geopolitical interests are at stake."

In The Guardian it was reported very differently. Like it was an arranged retirement and this was just his exit letter

Top UN official in New York steps down citing ‘genocide’ of Palestinian civilians

He informed the UN in March 2023 of his upcoming retirement