Your precious biodiversity is being protected by hunters.
How so?
Why? Because if they hunted them completely out of existence, they couldn't hunt them anymore. Self-interest, protection of the value of one's private property, has succeeded where environmentalism and the commons has failed.
If you think the above is an answer to my question of "How so?", then think again. It really only is demonstrative of your shallow understanding of what environmentalism really is, what diversity is, and what the goals of megafauna preservation are.
Do you know what the goals of megafauna preservation are? Because I can assure you, your example of a Texan hunting ranch are not satisfying those goals. Once again, we see where your smug responses are only indicative of your belief that you
think you understand what's going on, but really don't.
Are you by chance going to pick up a book on ecology yet? Or are you going to defend your ignorance because I haven't given in to your expectations that I explain it all for you?