What is a major reason why the renaissance began in northern and central italy?

The main reason is that city states were becoming increasingly wealthy

The nation was not unified and every city was a state for itself. This meant that they didn't have to think about the rest of the land and they focused on trading and getting richer and richer. The rich lords and ladies liked art and employed numerous artists to do commission work or to make the state a better place or similar things.

It covered the territory of land across eurasia from northeastern europe to the pacific ocean.