I think there were rumors about poison in his hooch or something, nothing really ever came to light on that, or it could've been just Yeltsin coming off a near-fatal bender and blaming Vlad seemed a good idea at the time.
But I think his ego could be turned against him, not sure he's up toe bear wrestling, but I would think some challenge to his manhood could be made placing him in a vulnerable position to be snuffed. I'd not shed one tear over such a demise, in fact I'd probably hoist some Stoli in celebration!