Sometimes, an animal exhibit is very good and always popular among visitors. The same animal in another zoo is just average, although exhibits are about the same size, the same price, and have nothing extraordinary. I wonder why? Do you know such very popular exhibits for average species? Or failed efforts?
Marwell has a whole host of these .... - throughout the transition from 20th to 21st century multiple exhibits at Marwell came and went - a decent jaguar enclosure which became progressively flimsy over the years and was decomissioned entirely in 2004, after the animals left. A children's farm to the north of the zoo I think had a similar fate - closing in 2006, and renovated for exotic fauna in 2007. This renovation too fell over time - exhibits in this area becoming less stocked, a walkthrough for Golden Lion Tamarin proving ineffective eventually, with the animals being moved out. It now holds Blue-faced Honeyeaters. A former pigeon-shed was converted to a small nocturne house shortly before the turn of the millenium... itself shut in 2007. A 'Rodent Room' [according to others here, essentially a poorly-lit glass-window with a variety of rodents - some species of which were very obscure] disappeared by 2006 - though now it is housing for Visayan Warty Pigs. [as an indoor area] A climbing-frame type thing for coati fell out of use in 2014 when a new enclosure was created; only for the coatis to be dispatched in 2018; the enclosure now holds red panda. An entire tropical greenhouse fell out of use in 2018; but in this case it was due to the opening of a superior, larger tropical house at Marwell. And perhaps more... But if anything, it seems that the worst of the 'Marwellian recession' appears to have finished, thankfully.
Speaking of Marwell I can think of one example there of the scenario the OP is asking for. This year they added Clouded Leopards to the zoo in an enclosure that previously housed Amur Leopards. This has since appeared to be a very popular exhibit, which surprises me as it is not a well known species. Interestingly another local zoo, the Cotswold Wildlife Park replaced Amur Leopards with Clouded several years ago and I don't recall seeing such interest in the species there. As to why, which is what the OP is asking. Marwell is promoting the Clouded Leopards within the zoo itself. They have large display boards about them as you walk from the car park to the zoo entrance and around the vicinity of the enclosure. Maybe this is drawing attention to their striking coat pattern and their elusiveness, which means visitors are returning to the enclosure in the hope they might get a peak. I can't recall Cotswold promoting them in such a way. A final twist is that I find them easier to see at Cotswold than Marwell.
