This seems like distinguishing between the snowflake that falls on a sheet of snow and starts an avalanche, and the snow that collects along the way. Both were necessary conditions for the avalanche, but is either more to blame? It's an imperfect analogy but my point is this: the problem is all the loose snow sitting on a slope in the first place.
Unless those first people were actively trying to create an insolvency crisis, it seems to me they were either being prudent or prescient. There's a reason it's called the "tragedy" of the commons, and not the "tyranny" of the commons.
