That's an interesting graph. They appear to have cherry picked data and used strange start dates for each. Based on numbers I've seen it looks more like this:
Bitcoin launched 1/2009 - as of now there are 100M users (your graph says 135M, which seems to be a very high estimate but lets go with that).
World Wide Web was released 4/1993 - 13 years later there were at least 700M users (very conservative estimate). Mind you this growth depended on everything from having a computer (22.9% of US households had a computer in 1993) to laying untold miles of fiber optics, undersea cables, building out physical datacenters, etc. Literally people digging ditches and ships circling the globe - many thousands of miles over.
By being essentially just another internet application (most people consider WWW = internet) taking advantage of all of this infrastructure Bitcoin/blockchain had/has a HUGE advantage over the WWW. To be a bitcoin user in 2009 you had to have a computer and install a program. To be a bitcoin user for the vast majority of its life you could/can hear about bitcoin at a bar, pull your phone out, and install an app on your smartphone to be a "bitcoin user" for next to nothing in under five minutes.
To be a WWW user in 1993 you had to have a computer that could handle it (Windows? Trumpet Winsock?, CPU, RAM, modem, etc) and a local ISP, etc. I remember in 1994 having to install a modem, a second phone line, and dial into an ISP that was LONG DISTANCE... It literally took weeks to get on the internet in 1994 and especially in my case, it was very expensive and very technically challenging (Hayes commands anyone? Chat scripts? PPP/SLIP?).
Then a little later America Online (still crazy expensive), maybe have it at work or university, or in the later years get lucky and have broadband in your area. I couldn't get DSL until 2004, for example (and it was still very expensive).
Even with all of these monumental challenges the WWW grew at least 5x faster than bitcoin (and it's really probably closer to 10x).
I suspected that was the case with Lightning. I'll keep digging into this because as I'm sure you can tell I'm fascinated with this. Overall I'm really trying to ask:
Why has adoption in the "cryptosphere" been so terrible (arguably the worst rate of any recent technology)? This is a question every honest blockchain advocate needs to ask themselves because there are clearly significant issues impeding mass adoption. Whatever these issues are need to be identified and rectified to the extent they can. I truly hope it's not the obvious answer - "It doesn't provide anything most people want or need".