Oh so many issues, neglect, subsidence of the grand entrance, Granada, neighbour issues leading to planning permission struggles, problems with their last big investment (flying island, the problems were more than just maintenance issues, again, neighbours complained constantly and very publically, going to the local press on multiple occasions,) broome ultimately failing with his plans, the list could go on...
But ultimately a string of misplaced investments, at a time when they had some momentum in the early-mid 90s, is what struck the mortal blow. Then a period of very little investment is when the life support was turned off altogether. Those last few years of 'changing direction to a more family focused park' were just the park's 'death rattle.' It's fate was pretty much sealed when Broome couldn't deliver and dropped out.
On the plus side, the houses are flying up on the site fast now, and it seems like we get more and more new regular customers each week.

(at least until we have to put prices up beyond the reach of normal human beings!!!)
If you're interested, this is a very good little documentary on the park, with most details included and accurate.