Man has to defeat greed, fear and hate first. To think a technology will do the job is naive wishful thinking. If someone threatens to kill my family, multisig isn't going to protect them.
Discussion
Let’s do a thought experiment: everyone in parliament holds a multisig key. A certain number of keys are required to authorize any transfer. As soon as the country is attacked, all these key holders disperse to allied nations. For an attacker to gain access to enough keys, they would have to locate all these allies. With a bit of imagination, there are many possible ways to protect a nation’s wealth with multisig.