But why would anyone else being able to deliver at the same time get anything less?

I agree there's actually an issue here, ideally the price should be set by the next seller which just didn't get to sell.

The cheaper suppliers actually bid with their prices, and why wouldn’t those prices be fair then? The EU then goes and gives them more than they offered. Make it make sense. Google „merit order“.

It‘s still a gamble for suppliers btw. The prices change every 15 minutes, and every cheap supplier is at the whim of more expensive suppliers.