Him engaging in emotional- and possibly sexual- affairs with multiple women? Yeah, it most certainly is grounds for divorce, but it not for the reason he thinks, and if the judge has half a brain, they sure as hell won't take that information as being in his favor. I suggest getting screenshots of the snapchats before he deletes them for evidence. While normally I would say that you were in the wrong for accessing his phone apparently without permission, in this case his breach of trust and actions against the relationship are so much more harmful that I can't really say that I do blame you for doing so.