Well, luckily, those who find the malicious activity are usually companies who do this proactively (for the good of the community, and understandably also for marketing). There are several who seem to be trying to be the first to announce, and usually succeed. IMHO it should be Microsoft (as owners of GitHub, owners of npm) who should take the helm and spend the tokens to scan each new package for malicious code. It gets easier and easier to detect as models improve (also gets easier and easier to create, and try to avoid detection on the other hand)