F1 Airboxes

I have a question about the airbox/roll hoop. At first I thought it was the 2017 reg changes but now I'm convinced the Halo had something to do with this change. Before, most of the airboxes were circular but in 2018 they got wide and many still remain that way. What was the motive behind the change, were there any benefits, and why does Ferrari use a triangle airbox now if there are benefits to the oval airbox? The pictures are Ferrari's 2017 and 2018 challengers.