If you must, I think it is more about the underlying cause versus the immediate cause.

Of course you speculate whether he would have been an alcoholic if he hadn't had a lonely childhood and hadn't had someone so close to him that died.

There is no "underlying cause" that can definitely pointed to, that's just hubris. You can't know that if those things didn't happen he wouldn't have still become someone who would drink themselves to death, or that if something else happened, such as becoming devoutly religious, he might have been able to avoid it.

Of course one cannot be sure that it is the underlying cause.

That's what my second sentence alludes to.