They counted on their chumminess with the Prime Minister, Rishi Sunak, who's been an outspoken supporter of Revolut. Iirc a report from Private Eye, there is a hint of an ongoing cold war between the PM's henchmen telling bank regulators to let them get the license, and regulators resisting - likely because nobody wants to be responsible for authorizing a business that clearly doesn't meet the necessary requirements in very obvious ways.