One of the major factors in the success of the YWP was their superbly-orchestrated 'rescue' of 13 lions from deeply substandard exhibits at Oradea Zoo in Romania.
As well as a dramatic improvement in the welfare of the cats concerned, the park also got a large new attraction and a large amount of very positive publicity in both local and national media. It led to a very good relationship with the press that still continues - there was a local TV special report when the first tiger arrived from Highland, for instance.
While there can be no doubt the cats are much better off now (the YWP lion exhibit is probably the best African Lion exhibit in the UK that you can't drive through), my own feeling is that the lasting effect will indeed prove to be the PR - it's placed the immensely promising YWP in a very positive light with the local population just when it needed to gain their support as a new venture.