Quick Question

As a re reader of your books for close to 15 years (yes I've got them
all) I've wondered about the rather dark turn your writing in Rise of
a Merchant Prince and what brought that on? Your books till that point
had a tongue in cheek humor and a hope to them but I find the dark
trend is growing in the continuing series (no this is not a criticism
on the series) I'm just wondering if there was a reason for this?
(...The worst lol a fan trying to delve in to the whys of creative
process but this is your historical baby so I thought Id ask)
Thank you,
Matt Jenkins