I recently came across a take about the Fall being metaphorical, something Will made up in his head to symbolise his ''fall'' from grace/into darkness and him accepting that he has ''fallen'' for Hannibal. And though I love love love that take, I can't help but love a canon in which the Fall was real more. Like, that fact that Will actually pushed them off that cliff, actively deciding he'd rather die with Hannibal than ever suffer a life without him again, that's romance. A sad yet magical brand of hopelessness and desperation that feels very fitting for the episode and Will's situation. Will was married, he actually tried for a new life, he tried to be a father, he did everything he could to ''escape'' from his feelings but he couldn't. He knew he still loved Hannibal and he always did, enough to come back to him in the end after saying he never wanted to see him again. Even worse, he didn't just come back to see him, he set him free, just to have H to himself one last time! Will made an escape plan for them just so that they could have one more night together! That's as good as it gets. Will really just left everything, everyone, behind to be with Hannibal. To keep them together the only way Will knew how to: by plunging to their deaths in each others arms.
There's no way Will could have thought they had a chance of survival, not with their injuries and the height of the cliff. He also knew the FBI would find them if they stayed in the house and tried to flee, so he chose the only option he felt was left for them: dying together. Mind you, if Will had stayed ashore, he wouldn't have been arrested. He could have handed H to the FBI without thinking twice. He was also in the position to just shove Hannibal off the cliff, carrying out the plan he promised would work: kill Dolarhyde, then Hannibal. But he didn't. He couldn't! He didn't have a plan. He thought that their embrace on the cliff was it. Will chose to spend his last moments with his head on Hannibals chest and his arms around him, listening to his beating heart. He couldn't stomach the idea of living without Hannibal, not again, not after everything that happened, so it ended up in Will pulling them over and Hannibal letting him do it! If he wasn't ready to die there with Will, he would have stepped away from the edge moments before. They both knew, and they were satisfied with their ending. Maybe it wasn't happiness, but it was beautiful. No greater ending than that for a pair like them.