Poverty. Land is quite good in Zimbabwe and there are a lot of farms. These had been given to people who were not able to run them so well. As a result food production dropped, which has led to poverty and hunger. Massive inflation has led to high prices, making it more difficult for people to buy food.
Robert Mugabe has run the country since independence in 1980 and during that time has become increasingly dictatorial in his style. There has been a lot of violence and civil unrest in the country.