It wasn't a festival - it was two gigs with the same headliner and multiple support acts. 75,000 people weren't buying tickets just to see the Charlatans and Cast.
And to be fair, I went to an actual festival in the late 90s that Robbie Williams played at, and many people stayed in their tents to avoid that shite!
Anyway, let's see how fast these tickets sell out, because I think you'll be changing your opinion based on that rather than what crowds they were getting 30 years ago.
Edit: And I don't have an agenda, other than the fact I think you're well off the mark about their appeal. I don't even like the band.