NYT says this switch to pagers has been recent, after the Oct 7 attacks last year, when Hezbollah suspected that Israel was spying on the cell network, and using it to locate targets for strikes. So all these pagers got distributed to Hezbollah-affiliated people in short order . This system doesn’t use commercial networks, and has been called a “closed” network by the NYT.
If all that is true, then that means anyone with one of these closed-network pagers got it from being involved with Hezbollah in the first place.