Why would an elite class of people or government want to collapse its own drinking water supply or financial system?

To control people through selective access to alternatives they've set up.

Headline of tomorrow, perhaps? Engineer Forced to Endure Twelve-Hour Scrum to Earn One Glass of Drinking Water in Gov't Pilot Scheme?

Because, if 'they' have a better system in place, that allows for greater control, they would want to move people to that instead. Just like how people are migrated from legacy systems to new ones.

The system we are meant to migrate to is ai-managed technocracy, with global governance (country governments will be adminstrative - they are that now tbh), central Bank digital currency (programmable, temporary credits - no cash) to allow tracking of everything, 'smart/spy' everything (phones, electricity, water) to allow for micro control of each individuals resource use.

'Saving the planet from climate change' is narrative that is in use to get turkeys voting for Christmas.