Why did the desert rat-kangaroo become extinct?

There is no known animal called a "desert rat-kangaroo". It's possible you're thinking of a different animal, or the name is a made-up one.

If you could provide more information about the animal you're asking about, such as:

* Where it lived: This could help narrow down the search to a specific species.

* What it looked like: A description of its physical features would be useful.

* When it went extinct: Knowing the approximate time period would be helpful.

With more details, we can try to find information about the animal and why it went extinct.