This is the first time this year I see an interesting thread/post, thanks for that.
1MB can be considered for preventing spam. Maybe he didn't think if bitcoin could become so popular and also there aren't some things considered like what will happen after
...if more than 1,000 miners are needed for Bitcoin...No amount of miners are needed for Bitcoin. Difficulty scales with the hashrate. The amount of miners is a result of people thinking Bitcoin has value.