No so strange really. Wealthy landowners with space and money to indulge their passions often collect things. Art, taxidermy, cars, live animals... Midland Bird Garden and Midland Motor Museum were on the same site. Broxbourne have a speedway museum. Stagsden Bird Gardens founder ran an upmarket second hand-book business and grew and exhibited pelargoniums. Some logic perhaps - as a common visitor group is often tri-generational, made up of a senior couple with the daughter and her children. The zoo visit will often planned be for the kid's benefit, but Grandad is the one with the wallet, and he is perhaps a bit bored by animals. He might even stay in the car for a nap and a read of the paper; so maybe he might pay the entry fee if there was something which interested him? Classic cars make a steady exhibit with good dose of nostalgia thrown in, they dont hide in the bushes, or die, they are instantly visible to the 15 second attention-spanners, they can be shut away for the winter, and dont need day-to-day care.