The circumstances for this are not unique to NPM. The popularity is what makes it so susceptible to these attacks.

It's not just the popularity, it's partly the update mechanism and partly the culture. In what sane world would you always pull in all the newest things, regardless or whether you need them or not? This is a default at build time for so many setups. If you absolutely must use that package manager, at least lock down your versions, and update selectively. I don't even know if that's possible to do with the dependencies' dependencies (and so on), or are people forced to just pull in whatever, every time.