Tricky, because they have satellite communications and they can fly pretty high up. I imagine there are redundant systems too, perhaps even a local ship or something for fallback. They're also not a RC plane which needs constant input or it will crash, I imagine if it loses signal it will fly according to internal programming. You'd have to jam all the gps systems it likely can tie into. And the Satellite comms (maybe more than one) and the backup long range radio comms (maybe more than one). And that's just a napkin theorized setup for communication, not including any potential secret sauce stuff they have on there.

IMO, they probably wanted a window of opportunity to do stuff that wasn't monitored by it, like launch an attack or move someone or whatever. It would take time to get another drone up and in position.

That definitely was a risky move by Russia though, assuming it was truly in international "waters" and we weren't crossing a line somewhere being extra nosey. We certainly would punish them if they misbehaved.