Most of these guys know that carrying a cell phone is putting a target on yourself. Soleimani may have thought the USA would never touch him, but he knew other folks with similar capability, like the Mossad, wanted him dead. Once Soleimani was killed, any high level person associated with anti-US forces would have to be an idiot to make that mistake.
My hope is that it’s option 2, that we have much better HUMINT among the Iran backed militias than anyone would have guessed.
Humint is great but Sigint and Elint rock.