That's not an uncommon response to when people finally die from a terminal illness. It's not particularly well-known, but a lot of doctors simply refuse treatment for terminal illness and prefer to preserve their quality of life for their remaining time. But, of course, dying either way isn't particularly nice: apparently a lot of doctors fear not getting a terminal illness, since dying from old age is much more draining.
Just my two cents, though. I'm sorry for your loss man, I have no idea how close you were but somehow losing a grandparent seems like a particularly painful experience. Hope you're doing all right.