What factor would have most likely prevented the problems that cities faced during urbanization?

The answer to the question is a slower transit towards industrialization. In the industrial period, cities grew tremendously with the onset of new technologies and prospect for families making a new living for themselves. Unfortunately, the cities grew too fast and couldn't hold the influx of people living in them. This led to tremendous pollution, famine, disease and war. With a slower growth, the cities would have been able to better handle the influx of new people.