Just to add to this, digital payments in India got popular well before COVID, significantly increasing after the demonetization charade (which imo was a bad decision and total chaos).
COVID might have convinced few people that's all.
Demonetization's effect is not clear since UPI came out just a year before Demonetization took place.
It took off because of young generation and costs nothing as simple as that. They forced businesses and other to embrace it.
Fun fact, i have been using UPI ever since it came out and used to pay for coconut/veggies with it even back in 2017