I am only making an assumption about this here, but I believe what this graph represents is interest in forex going up as people thought it was so easy (and way better leverage).
However, people failed.
The interest from the beginning and the end seem to be about the same. I think there was a heavy push to educate people in this field (which didn't work obviously).
I know someone personally who overlooks a hole on a golf course of a gated community because he can wake up and within hours make $$$$$. He can also lose that too, but it's usually a win for him because he sees trends.
Interest will always remain in forex. People also day trade cryptocurrencies too.
All sounds familiar, like domaining, eh?
I've made money in this niche and hold a few good FX domains with some sales under my belt, and still interest in those names.