Separatist and criminal gangs are a real problem in the Philippines hence the support. People vote for the demon slayers when their system is threatened. The threat can be real or imaginary.
He is pretty much the Philippine version of Trump, an anti-establishment campaigner, waging a war on criminals (particularly, drugs, since it is apparently a national issue). He is still leading surveys despite of what he has been saying and an anti-establishment but unlike Trump he will probably win.
Look what happened in Poland, Hungary, etc in recent elections. Polish leader claimed immigrants will bring "strange diseases", declared "Christian Republic of Poland" and still won big
Sometimes it is hard to explain how most of the population thinking process work. For instance, the Mongols who still hold Genghis Khan in a quite high regard despite he was the destroyer of civilizations. The guy was responsible, either directly or indirectly, for the deaths of tens of millions of people, plus the irreparable destruction of countless cities, regions and cultures, some of which were the most glorious in the world. He was among the greatest villains in history and pretty much killed every enemy who stood above the height of a wagon wheel and while he is the only person on the Mongolian tugrik for all denominations starting from 500.
Let's hope this Philippine populist has more sense than his loudmouth.
I highly doubt. He appeals to many because he speaks his mind in a completely uncensored manner.