I don’t think covid cured the flu, It’s there’s still, flu A and B circulating. But lockdowns and not working and socializing had an effect (along with zero chinese tourists). Covid went from a 1 to 2 infections to a 1 to 5 infections while flu stayed at 1 to 1. So even with reduced contact, covid would spread faster than flu.
https://www.cdc.gov/flu/symptoms/flu-vs-covid19.htm
Actually, according to the numbers, covid spread wildly while flu was halted! (Mortality - The PIC mortality rate is the rate of deaths attributed to pneumonia, influenza, or COVID-19. This year, the majority of PIC deaths were due to COVID-19. 646 deaths were attributed to the flu.) If masking, distancing, and lockdowns halted the seasonal flu why didn't the same happen for covid?