There's selection bias at play here.
I didn't play last weekend because I didn't think I could compete this time around, and I'm a top 25ish% player per my K/D. My scrubbier RL friends will never play Trials because they don't think they can ever compete. What you see is 16% of the players who self-select into the most competitive multiplayer mode, which is not representative of the entire player population at all.
If people don't even enter to try for the lower rewards then they're not really the target audience for Trials.
If 800,000 people tried out ToO, and we know Destiny has 25M registered users, then 3% of the population played trials.
On top of that. .4% made it to the Lighthouse.
It's not .01%, but it's not exactly a big number...
Sure, if you're considering all the 25M to be PvP players. I'd be really curious to see regular Crucible numbers across the week and comparing that to Trials number, rather than registered users in a game that's traditionally been more PVE oriented than PvP.