Certainly as late as the late 1980's & if we go back further, our record home attendance is an fa cup tie, the highest attendance at the swamp is an fa cup tie (between Wolves and Grimsby iirc) & many other clubs will be the same, so for many years, the cup was more attractive to fans than the league, however now it's the other way round (& for some appears to be an irrelevance, or an inconvenience).
For me, it's sad to see what used to be such a fantastic competition relegated in people's affections in this way, & was wondering why others thought this has happened, or to point out how it is still the same competition it always was.
(I also note the sparse crowd at the Cardiff game on now, & Birmingham seemed to have about 5,000 less than normal despite 4,500 travelling fans, which I doubt Brighton or Brentford brought to St Andrews).
Not a slight about any club, but about the competition in general