There are tons of data available. Even at a layman level, it should be pretty obvious that doing no or late lockdown ends up in situations where there are large numbers of deaths.
Even this is debatable.
I have no skin in this game and no strong opinion, but let's be honest -- lots of people were expecting total disaster in Sweden since they decided not to implement lockdown, but so far their daily cases chart looks not that different from other nordic countries.
That's because many people in Sweden live alone.