Eliminating player A can be achieved by any means including manipulating the board into killing them, manipulating bots into killing them, feeding them, or targeting them yourself.
I understand that the current mode of player B kills player A, player C (who died three turns ago) wins because player A was their mission seems ridiculous but it is a valid game mode, it is what we have now and exploring the implications of that rather than immediately demanding that it be changed can yield some interesting results.
For example I had never kill guarded by sacrificing troops as cannon fodder in the forms of swaths of my 1s carefully left as I sweep around the board creating separation between all the players I don’t want near each other, but over the last two days I have used that tactic several times testing against bots when I had a large number of territories mission or multi continent mission that I could not complete immediately but the death of multiple players was imminent.
Also the hilarious routing of trying to take two continents on the classic map or 28 territories while not killing anyone often having to manipulate the bot to take some additional territory out of the bonus so you could take it on a later turn without killing them are all new experiences on the risk board for me.
holding SA… Routing a take on the continent of Asia so as to only kill a player on the last territory take so I won before the kill triggered someone else’s win all the while not knowing what would happen since the mode is in beta and who knows maybe the kill would register first. 😂