Your points about interest are undoubtly true, however the correlation between interest and price is not really that clear.

In the second half of 2017 crypto prices where skyrocking and so was the interest in cryptocurrency. However one might argue that the rising price was driving the interest into the topic rather then the other way around, because the recent "crash" in february was not correlating with a suddenly dropping interest. Now after some weeks of limited price action we are seeing a decrease in interest, however we do not see a decrease in price. (At least this holds for bitcoin) If Bitcoin was to suddenly increase a lot in price again (or even decrease) this would very likely increase the interest again.

So in conclusion I am arguing that interest in cryptocurrency is not a good metric to "forecast" price evolution as the correlation between those two is rather unclear and judging from past events it seems as if price action is dictating interest rather more then the other way around.