It's very hard to protect someone from a virus that's jumped the animal>human barrier for which no one on Earth has any resistance, and for which there is very little treatment or even guidance available aside from individual isolation, and even that can be random. Hard to wrap your head around something invisible that can kill you after a trip to Trader Joe's.
I'm very sorry for his and your loss. I've lost a lot of people over my time and I can only relate the two things that became apparent and ultimately the same two things that got me through, and believe me, I know, it's NEVER easy:
First, I always felt if it were up to me, they'd still be here . . . . but unfortunately, it's not up to me.
Second, I found the only 'sense' I could make of it was that their passing was part of a plan that I will never be privy to, and only through my faith could I accept their leaving: They're heading for something far better than this world and it was their time to go there.
I learned these things the hard way, and just possibly, they may help you and your friend.
All the Best,
JW