Although these bots surely ruined their income, there's also other factors to why they were banned (for sure). Some do tend to abuse a bit by posting more ads on their respective pages than the limit imposed by adsense, some do use two adsense accounts so they could use more of their ads on a single page (an issue that has started since a month ago that these faucets had their accounts banned by adsense too). Sadly the fix to these types of problem (bots), it's easier said, than done since for some reason, no matter how many types they alter the codes for securing the faucet against bots, the programmers always find a way to bypass it and it seems anything automated would have the same effect unless everything is check and done completely manually (in which no one has the time to do it).