> Some variant of this kind of disaster with smart contracts seems to do the rounds on Twitter every couple of days. Why does this keep happening?

Because it’s code which means errors are a fact of life, and the goal of crypto pushers was to spread the scam so instead of looking at formal methods in order to make “smart” contract ironclad, they started from ECMAScript so that any idiot could go from a frontend widget to deploying a smart contract with minimal introspection or reflexion.