In 1979 5 of the top 10 were hard rock with 2 more borderline hard rock but definitely what would be considered classic rock now.
In 1980 the top album was Pink Floyd “The Wall” definitely a hard rock band.
In 1981 the top album was REO Speedwagon’s “High Infidelity”. A hard rock band.
In 1982 the top album was Asia “Asia”. A hard rock band.
Seems to me hard rock was pretty dominant at that time. But I was just a teenager then so maybe I don’t know.