Actually, I think that decision probably went something like this:
Producers/Scriptwriters: Okay, Professor Aronnax, Captain Nemo? This is a Disney movie, so we’re really going to have to ask you to tune down the romance novel vibes, understand?
N & A:...Yes.
N.: Bah. The harpooner is pretty but also clearly stupid, and the assistant is just an obstacle… Professor Aronnax, though… Yes. You I’m keeping.
Producers/Scriptwriters: Dude, what did we just say?
N. & A.: Sorry?
Producers/Scriptwriters: You so totally aren’t. Okay, we’ll try this again.
N: *rescues Ned and Conseil from a shark*
A: *reaches out for N, almost as if making sure he’s not hurt*
Producers/Scriptwriters: Darn it, this just isn’t working. We’re writing you two out.
N. & A.:...How?
Producers/Scriptwriters: We’ll think of something.
This is so totally what happened. I believe it. I believe it.