Good thing lions can't swim.
[ While I kinda agree that ‘lion-ranches’ in the US might help the population...can you imagine the anxiety in most American urban areas if you brought this up? Even if you went ultra-rural into Tennessee...someone would eventually make up a anti-lion-ranch measure and require millions in fencing to convince the public it was safe.
Even in Africa....if you consider that roughly 250 people a year die from Lion attacks....there’s not a thrilling amount of support from the local populations over lions expanding their base and population. If you merely doubled the current Lion population in Africa....you’d probably see well over 500...maybe even 800...people killed. Who wants that? ]
Maybe a “Lion Island” would work better, take a Caribbean island that is more grassy than tree-ey and build a giant Lion habitat there, like Jurassic park...
Good thing lions can't swim.