The plant had the license, and authority to continue operating.

This was an economic decision of the follow-on owner, Entergy, subsequent to Boston Edison's sale to Entergy, deciding to exit. Entergy had received a license extension in 2006, relicensed through 2026, but exited in, 2019, not even bothering to take six more years of operating income on the plant.

Entergy transferred to a decommissioning organization, and exited the merchant nuclear power business, fulfilling its corporate plan to divest itself of merchant nuclear assets. It continues to operate nuclear plants in its home utility territory in Southern US.

References.

"Accelerated Decommissioning of Pilgrim Nuclear Power Station: A Progress Report." Power Magazine. March 2022.
https://www.powermag.com/accelerated-decommissioning-of-pilgrim-nuclear-power-station-a-progress-report/

Entergy completes plan to exit Merchant Nuclear operations
Energy Corporate announcement https://www.entergynewsroom.com/news/entergy-completes-sale-palisades-power-plant-holtec/