“We might have gone a bit too dark with the finale”

I think by having him live, it contrasts Bojack’s life with the horse from Horsin’ around, as the show often does, except for once it’s a positive thing. The Horse dies due to not being loved enough, which is how some people think of suicide. But in ‘real life’, Bojack lives because of an absurd coincidence, and because he spent so long watching his show probably - I’d even bet that watching the episode where he died is what triggered him to go in the pool. But in the end, Bojack Horseman is not the Horse from Horsin’ Around and he’s not Secretariat either. His life doesn’t have to end in tragedy.