One can’t really say fearmongered because drugs had always been a major issue in the country even before the Duterte administration — just never really reported well on. Unless you’re in a sheltered upper class family, stories of drugs ruining youth lives or gang-related fighting or the occasional murmur about syndicates, are not uncommon in the Philippines.

As you pointed out, some drug dealers have acquired so much wealth and influence over their control that it would be practically impossible to remove the problem in this manner. The former president attempted a very straightforward solution that helped him deal with the problem in the city he was once mayor in, but national politics is obviously very different.

He failed to alleviate the drug problem that way and should definitely be investigated for allowing collateral damage (which is acceptably understandable given that governments should always minimize unlawfully killing its on citizens without due process), but his solution reflected the general perception of anarchy faced by the general public in the Philippines — especially in the less well-off cities in the provinces and even the slums of Manila. His mixture of charisma and his harsh yet (brutally) logical attempt to rid the problem is the reason why despite this, he remains incredibly popular in the country (and probably won another term if the constitution allowed it).