I don't think today's attendance 'proves' anything. However, it may be indicative of the fact that Sunderland fans have bigger fish to fry than to pay to watch a televised cup tie against Southampton, who they will have played in the league twice by the end of the season. Sunderland fans may...
No, it was with the FA's backing. And the talk of the FA Cup losing its sparkle came years before 2000. Together with the return of English clubs into European competition, the lack of memorable finals after 1991 was probably a bigger factor in the FA Cup no longer being seen as a showpiece event.