Google trends is not good for this kind of analysis. Google trends is based on the number of searches for a particular term relative to all other searches. So you see the same trend when you look at other tech topics like Linux, programming, SSH, computer science, etc. It's not that these things are necessarily becoming less popular, just that tech oriented people were over represented on the early internet, and thus Google search. As more non tech people started googling stuff, tech topics fell in their relative importance.