Why not?

surely most of the sudden increase in the fan base would have come from Bradford ? or am I talking out of my rear end again ?

So you are saying that Keighley were sustainable because the majority of their fanbase was made up of kids? Right.

Their "fans" quickly went back to Bradford when "Bull Mania" started too.

Well am not sure how big Keighley is in terms of population, so hard to say really...

Yes, because it's on their doorstep. They wouldn't have to travel over 3hrs for every away game, like we do.

What I meant was that a lot of kids want to watch SL rugby. This is evidence at Rovers. Before SL our fanbase was (I would say) predominately adult, but since promotion to SL you now see a lot of young people wearing our shirts and supporting the club. If Keighley had been granted an SL place they would have built on the big fanbase that they had in the second tier, and not lost a lot of kids to the Bradford bandwaggon.
Put it this way, they brought around 2000 to Craven Park for a Friday night game. Quins on a Sunday afternoon bring about 1/10 that.

In that case then they would have been more valuable to SL - if they took 2000 to Bradford, Leeds, Cas, Huddersfield and Wakefield (at say £12 each on average) that's £24,000 they would have contributed to the income of each club.

That isn't exclusive to Hull KR, the same could be said for any club in this era.

(There is no way I am having that Keighley took 2000 to Hull on a Friday night unless a non-Hull KR supporter verifies this claim )

That isn't value to SL is it then, its value to a teams coffers for a tiny proportion of their overall income during the season.

2,000 is an unrealistic figure. The tiniest amount of income that would bring to the clubs, is nothing compared to the loss of sponsors and TV income that would be lost to the game, if it was solely M62.

Still not having it. Keighley struggled to get more than 5000 at home, never mind 2000 away.