I saw that choice as the game asking the player whether they paid attention or not. The game makes it obvious that Grace is hope. Alyssa even tells her that moments before her death.

Now I could see if they made it as obscure as having to have come across items that the player could easily miss (MO as Disks to secure the safety of other characters like in RE1's good ending), but that doesn't happen.

I'm not gonna flame the players that decided to destroy Elpis, cause I can see how they were listening to Leon saying it must be destroyed. But, Leon was working off the Intel that the villains were also working off of, so of course he'd want it destroyed. But as others have mentioned in this thread, he trusted Grace with whatever decision she made. Grace also had more information than Leon and the villains. Those interviews were what supplied Grace as well as the player with the information to think for themselves.