original: Edo consequently rapidly grew from what had been a small, virtually unknown fishing village in 1457 to a metropolis with an estimated population of 1,000,000 by 1721, the largest city in the world at the time.
simplifications: Edo quickly went from being a small, unknown fishing village in 1457, to a metropolis by 1721.  Edo had a population around 1 million and was the largest city in the world at the time. Edo grew from a small, unknown fishing town to a metropolis of 1,000,000 people from 1457 to 1721. It became the largest city in the world at the time. That's why Ed became a big city with 1,000,000 people by 1721. it was the largest city in the world at the time. Edo rapidly grew from a virtually unknown village in 1457 to a metropolis with a population of 1,000,000 by 1721. Edo rapidly grew from a small, unknown fishing village in 1457 to a metropolis with an estimated population of 1,000,000 by 1721. It was the largest city in the world at the time. As a result, Edo quickly grew from a small, unknown fishing village in 1457 to a city with around 1,000,000 inhabitants by 1721. It had become the largest city in the world at the time. Edo grew from a small fishing village into the largest city in the world. Edo therefore grew fast from a small, unknown fishing village in 1457 to a capital with a population around 1,000,000 by 1721, the largest city in the world at the time. Edo was a small fishing village in 1457, but grew to be the largest city in the world, with a population close to 1 million by 1721. Thus, Edo grew fast from a small, in effect unknown fishing village in 1457, to a metropolis with an estimated of 1,000,000 by 1721, the world's largest city at the time.