"More than 60% of all “potentially harmful applications” (PHAs) were caught with machine learning algorithms"
That still means 40% went through, if you believe Google even knows the full amount of malware delivered through the Play store. That "60%" might only be 20% or 40%.
With as much money as Google has, they could invest a lot more in checking the apps available through the Play store. There have been too many instances of apps that also came with malware payloads, and they should devote a lot more resources to investigating & stopping them.