The article is about what they are. Not why they are good or important. Tons of material out there is rambling on about them. Apparently a lot of smart people think they are good and important. But, it's rare that someone explains them clearly without putting on a thesis-defense writing style.

Monads avoiding double-containering is nice because you want to be able to use them a lot without finding yourself working with an Optional<Optional<Optional<Optional<Optional<Optional<Optional<Optional<bool>>>>>>>> at the end.