FWIW last time I was in El Salvador someone stole the phone of a friend I was with. Not too dramatic: they just grabbed it in a crowded area. But goes to show the crime there is definitely real.
That said, it is true that the crime rate (esp murder rate) has been massively reduced in El Salvador compared to what it used to be. They've arrested tens of thousands of gang members in a massive crackdown, and it's worked.