slow enough for block propagation to work properly in a global network and the cost to run a full node for "normal users" not getting too high too fast due to storage tech not keeping up
but fast enough to not stall transactions confirmation.
It’s kinda impossible to prove that 10 minutes isn’t arbitrary. It could have been 5, 7, 8, 12, 15, etc.
Fast enough to not stall transactions is not valid when talking about 10 minutes. They chose that specifically with the intention of building layer 2