Yes, they were. Very much so.
Did you know that Chelsea had an average attendance of 30,850 as far back as 1907/08?
Their rankings in terms of average attendances for some of the early years of the Football League:
1907/08 - 1st
1908/09 - 2nd
1909/10 - 2nd
1910/11 - 3rd
1911/12 - 1st
1912/13 - 1st
1913/14 - 1st
1914/15 - 3rd
1919/20 - 1st
1920/21 - 2nd
1921/22 - 1st
1922/23 - 4th
1923/24 - 1st
1924/25 - 4th
1925/26 - 1st
1926/27 - 5th
1927/28 - 3rd
1928/29 - 6th
1929/30 - 6th
1930/31 - 2nd
In 1925/26, Chelsea topped the national attendance charts despite playing in the Second Division. The only other clubs who have done that are Manchester City (1927/28), Newcastle United (1946/47 and 1947/48), Tottenham Hotspur (1949/50) and Manchester United (1974/75).