SPOILERS FOR THOSE WHO HAVEN'T BEAT THE GAME YET
...Because the real and only true Anders would have more likely caused all the final mess with a prank like this than with a Rico-like explosion. And Varric, as BioWare, likes to put a little drama llama in the story (*cough*Carver/Bethany*cough* "All that remains" *cough* Marethari *cough* that's a bad cold I got...

).
I have another one like this ready to be drawn, as soon as I figure out a good way to translate "preso per il culo" in english... and yes: emememe strikes again...

Mithbuster style!
Wanna come to the sewers help me collect crystalizated pee?
'K why not. Just let me fetch my gummy boots.