The 61,000 figure is an estimate, as the 8,000 number is likely underreported, and they use a number of statistical methods and data to arrive there:
https://www.cdc.gov/flu/about/burden-averted/2017-2018.htm
There are about 81,000 COVID deaths so far, and those numbers are ALSO underreported for a number of reasons.
https://blogs.scientificamerican.com/observations/comparing-covid-19-deaths-to-flu-deaths-is-like-comparing-apples-to-oranges/
The flu has a vaccine and a 100 year history of treatments, and is less contagious that COVID.
COVID has none of those things, and those large death numbers happened despite social distancing and other measures, where the flu in 2018 did not have that.
The public is far more able to protect itself against the flu.