Why do people think multiple people are going to survive? It has always only been 1 winner.

The games are specifically designed to have one 1 winner at the end. As we saw in season 1 even if multiple people make it until the last game, the game will always be a "to the death" last man standing wins.

We've even seen in the records that it's always 1 winner. Multiple people are not surviving season 3 and these games unless the games themselves end. The game makers make sure it's only ever 1 at the end.