One of the big reason for banning flights from India is that they don't trust the test results shown by Indians to board the flight.
This is the news from first time the ban was put in place.
https://www.reuters.com/world/ameri...ghts-could-soon-make-announcement-2021-04-22/
Canadian Health Minister Patty Hajdu said that while Indian citizens accounted for 20% of all international arrivals, they represented over 50% of the positive tests conducted by Canadian airport officials.
And I know from acquaintances that people in India were getting fake Covid test results to board the flight. The numbers were just too big to ignore or just to say only few people were doing it.