Clever architecture will always beat cleverly trying to pick only one cloud.
Being cloud agnostic is best.
This means setting up a private cloud.
Hosted servers, and managed servers are perfectly capable of near zero downtime. this is because it's the same equipment (or often more consumer grade) that the "cloud" works on and plans for even more failure.
Digital Ocean definitely does not guarantee zero downtime. That's a lot of 9's.
It's simple to run well established tools like Proxmox on bare metal that will do everything Digital Ocean promises, and it's not susceptible to attacks, or exploits where the shared memory and CPU usage will leak what customers believe is their private VPS.
Nothing ever failing in the case of a tool like Proxmox is, install it on two servers, one VPS exists on both nodes (you connect both servers as nodes), click high availability, and it's generally up and running. Put cloudflare in front of it like the best preference practices of today.
If you're curious about this, there's some pretty eye opening and short videos on Proxmox available on Youtube that are hard to unsee.
When you have 2 nodes running, both are mirrored and running, one can have hardware break.
Also, hardware can provide failure notifications before it breaks, and experience teaches to just update and upgrade before hard drives break.
Since tools like proxmox just add a node, you add new hardware, mark the VM for that node to mirror, and it is taken care of.
Terraform etc can sit below Proxmox and alleviate what you're speaking about:
Some examples: https://www.youtube.com/watch?v=dvyeoDBUtsU