So what I would say to you is that when you say "eating large quantities of sugar is a factor [in developing diabetes]" other people, including me, say "too much sugar can lead to developing diabetes" and mean exactly the same thing.

If you want to be precise, you can qualify phrases like "can lead to" and "cause" and so on with "directly or indirectly" - but to me, without that qualification, they can mean either.

Cheers!