Both pedals being on the same side are a relic from when

1. We needed a third pedal for the clutch
2. Pedals were directly mechanically connected to their functions so there was a danger of pressing both at the same time

Neither of these are true anymore. Modern cars are automatic and can and do just disengage the accelerator if the brake is pressed.

With electric cars they're doubly untrue. There is not mechanical connection to speak off, and many drive use only a singular pedal most of the time.

On the flip side there are quite a few benefits to to having them on opposite sides:

1. There are an estimated 16,000 crashes/year in the US alone due to pedal error. This would decrease if they weren't y'know, right next to each other
2. Especially in stop and go driving, this would significantly reduce ankle/leg fatigue as it would be spread out over both legs
3. Reaction times would be improved as you can push the brake directly, you no longer have to move your leg over from the accelerator.