Both Wiens and MG said a supply-chain attack in which a remote-triggered explosive was surreptitiously placed into the pagers before they were distributed is more likely. There is precedent for this: in 1996, Israel put a bomb inside of a cell phone and used it to kill Yahya Ayyash, who was then a bomb maker for Hamas.
What I find most concerning is that a large number of people/journalists considered it plausible to blow up a (edit: stock standard) pager remotely via some hack or zero day.
The war crimes are expected.