The problem with that chart (with respect to your interpretation) is that it deals with search volume relative to itself.  The peak is simply the highest it has been, but it's not a value.  The only thing that chart tells us is that ~5x more people compared to today searched for those terms at its peak.  Do you think that all those people that searched back then suddenly forgot about Bitcoin because they haven't searched it again?  Search volume spiked because a LOT of press was released very close together.