Barry mucking with the timeline?
I'm not certain they will be able to explain it satisfactorily, but by god, he definitely has the motivation in there deep rooted.
First Oliver takes his youngest daughter to her "death" at sea, he then returns from the dead - Sara does not. This also breaks his eldest daughters heart, as she lost both her sister, boyfriend, and was betrayed. So Quentin has a failed relationship, a dead daughter and a broken hearted one, and is an alcoholic.
Then his youngest daughter returns from the dead. Sweet *****. And then, due again to being in the presence of Oliver, he loses his eldest daughter, AND his youngest daughter is off in the timestream - it's not like she is popping home to say hello much.
Not to mention he carries out activities that put his job and livelihood at risk, before Quentin came in on the team.
Oliver is responsible for a lot of what happened to Quentin over the years.
There is a lot to dredge up.
I really hope it isnt split personality/meta personality due to Flashpoint. I just feel like it's too contrived.