I think we can all agree this attacker was sophisticated. But why would a government want to own tons of random Linux machines that have open sshd mappings? You have to expose sshd explicitly in most cloud environments (or on interesting networks worthy of attack.) Besides, the attacker must've known that if this is all over the internet eventually someone is going to notice.
I think the attacker had a target in mind. They were clearly focused on specific Linux distros. I'd imagine they were after a specific set of sshd bastion machine(s). Maybe they have the ability to get on the VPN that has access to the bastion(s) but the subset of users with actual bastion access is perhaps much smaller and more alert/less vulnerable to phishing.
So what's going to be the most valuable thing to hack that uses Linux sshd bastions? Something so valuable it's worth dedicating ~3 years of your life to it? My best guess is a crypto exchange.