The problem with using those numbers as-is as an indicator of game system popularity is that Roll20 sucks for non-5e systems and a lot of people have jumped ship to Foundry VTT [1], which has much better mechanical support for various game systems.
A someone who currently plays in four weekly games, I don't know a single person that has actually switched from Roll20 to Foundry, despite me recommending it and everyone agreeing it's the superior product in many ways.
Roll20 still has the overwhelming supermajority of the VTT market, Foundry is the Linux of VTTs.
I play PF2e and the entire community seems to have switched from Roll20. At least all of the DMs in the online living world I was part of, my regular games, and all of the PF2e games I see listed on various LFG subreddits.
Some of us use d&d beyond with it, some not. I think the dungeon master prefers foundry much more than roll 20.
What it took was the dungeon master saying we shall do this, a session or two to work out the kinks, and one other player who gained expertise enough to explain game play mechanics (e.g., use the x key) to the rest of us (to offload some of that burden from the dungeon master)
The methodology for these numbers changed in Q2 2019[1], so I don't think it's safe to compare 2014 numbers to 2021. However, Q2 2019 is well before FoundryVTT exited beta, so it is safe to look at the 2019 numbers and draw conclusions about online play:
[1]: https://foundryvtt.com