Whoever paid for that grenade doesn't trust the soldier / mercenary they gave it to very far, that's why the network connection exists in the first place, hackers can exploit that.
This shows how hard it is to write sci-fi when I was joking about "grenades as a service" - someone's gone one better and made a wifi mesh network of landmines!
And then converted the landmines to remote-operated as part of a legal fiction about victim-operated devices. Which is the military version of the concern about robots taking jobs: to what extent is it acceptable to have munitions making their own decisions about taking lives?
Anyway, in the Shadowrun universe you'd definitely be able to hack the mesh network of landmines.
At least that's the reason I just made up.