Urban - rural migration as people are frustrated with city life. Noise, traffic, pollution, crime, vandalism etc, usually labelled as “push and pull” factors. You can look at the Lee Migration Model.
People who are ageing and retiring may want to live somewhere else which is quieter/ more peaceful for a different pace of life. An older person has different needs of a place and want a more community aspect of their living, such as a local pub or community centre, as opposed to a young person.
People who are having families want larger, rural or suburban houses. City centres usually have small apartments catered for single people or couples, not usually for families. Suburbs have more familial opportunities with schools, and are perceived as “safer”.
Other more crude ideas you could talk about disease or climate change. Lots of Jakarta is sinking as the clay is built in subsides due to costal erosion and overabstraction of ground water to provider for a sprawling population.
In Port-au-prince in Haiti the 2010 earthquake destroyed half of the built infrastructure and the remaining buildings were unsafe, so most of the population were housed in refugee camps outside of the city.
https://www.nytimes.com/interactive/...g-climate.html Useful case study about Jakarta.