Do you think this is a stupid idea or do you think I'll get closure?

Before I do it I need your opinion:
I was thinking of e-mailing the guy I used to like’s ex-girlfriend from a few years back (I don’t know here she doesn’t know me) asking her why they broke up for example if he cheated, or if it was his fault.
I have no idea if this is a good guy or not and I’m so confused and just want closure and I’m hoping what ever she says will give it to me.. what do you think?