I wonder whether there would be also other options, but one very important aspect is the smog: the city center is where many industry-relevant things meet: the factories are all around it, transport, cars... and since it is surrounded by bad air, the air takes longer to dissipate. This is especially visible if the city is in a valley, such as Mexico city foe example.
Economic problems for many countries in Europe in the 1920s and 1930s were mainly caused by "<span>B. World War I," since this war left many countries torn apart in terms of their economies. </span>
