This seems like a straw man. Maybe they thought it was the "fairest" way to do things but that seems somewhat implausible. Does "fairest" even exist?

More likely they thought it was a way to distribute coins to a very wide swath of the cryptocurrency community. I doubt seriously anyone believed that some participants with very large numbers of addresses wouldn't exist, but by distributing to every non-dust address that meant that at least some meaningful number of coins was being distributed to each of a huge number of participants.

If they did believe there wouldn't be people with many addresses, well I guess you can't deny stupidity.