It's not like we haven't had people prank call the police on others. But 1. the number of false calls is rising, 2. probably because fancy new anonymizing services are making it very hard to find out who's making the calls, and 3. it's far more dangerous than previously, since SWAT has been taking over for more and more traditional police calls.
It's now turned into an intimidation tactic against people's [small-time] political opponents, and police haven't caught on yet. And even those that are aware have no good way of legally or practically dealing with it.