If that was the case then they could just stick 100 people in a lobby and get them to square off 1v1 in a tournament until there’s one winner.

And you think battle royales have too much down time?

I don't play them because they're all prey to the modern aggressive cash grab bullshit most online games are, but most of the downtime you're discussing is actually active and engaged. You need to be consciously making a decision during the parachute part to decide where you want to land. All the "collecting" is constantly under stress, because if you aren't aware of your surroundings at all times, you could be dead. The whole game mode has a tension to it that most others don't, because dying in death match doesn't cost you anything but 10 seconds to respawn.