Who made the decision to make the ending completely inaccurate and why?

The internet has lots of different versions of the way Lombard died and where Gable was when it happened. I've read many versions of the truth including Gable needing to be held back from climbing the mountainside where the plane crashed to save Lombard (People Magazine).

We know that Gable didn't start his service in the military until about 6 months after Lombard died.

Were the filmmakers just sloppy with the actual facts or was there a decision by screenwriter/director to create a sappy ending just to tie it up?

Why not just stick to the facts. I think they're much more interesting.