I'm not sure about Decentraland specifically, but typically there will be a subset of the DAO members who actually control the DAO treasury in a "multisig wallet". Say they have 10 signatories, they might have a requirement that 8 of the 10 signatories approve a transaction to either send ETH to Blender, or do the necessary swaps to give Blender USD. The signatories have committed to execute the will of the DAO.
Voting happens "off chain" using a tool called Snapshot (https://snapshot.org/#/snapshot.dcl.eth). If people hold some Decentraland tokens/assets, they can vote, and their vote is weighted in proportion to their holdings. This isn't without its problems: https://vitalik.ca/general/2021/08/16/voting3.html
If you want to learn more, I wrote a blog post on DAO tooling 101: https://blog.juicebox.money/dao-tooling-101/