My younger brother drugged himself out of a career, multiple jobs, thru three failed marriages, bankruptcy, and a couple of drug induced auto accidents...
Meanwhile we bailed him out literally and financially several times, tried to get him into rehab and stay clean all to no avail until, still and always totally in denial, he finally OD-ed at 54...
He sucked us all dry emotionally and financially until in the end we were reluctantly forced to accept he did not want help...Often there is no lie they won’t tell, scheme they won’t pursue, or offer of help the addict will accept unless it enables the continued substance abuse...Our family’s story is by no means unusual...
I am sorry for your loss.
It is my theory that these drugs destroy the mind’s problem solving and decision making functions. With that ability gone, they cannot chose to do the right thing that will protect them from further damage. This inability also does great damage to other since they cannot choose to do the right thing. It is very much the same effect as rabies to the mind of a dog.