Throw in the fact that Barry broke the timeline thanks to Flashpoint, and the recipe may have been exactly right to give Quentin a villainous alter ego of which he may not even fully be aware of.
Quentin could actually make a twisted sort of sense as the man behind the Prometheus mask.
Thea has mentioned that Quentin has been missing work a lot, and some of those days coincide with attacks from Prometheus.
The combination of grief, heartbreak, stress, and copious amount of alcohol could have led to a Arrow-style psychological break for Quentin.