>>1986178The bridge is for the benefit of the whole island, which isn't uniformly underdeveloped and corrupt. The national government, the EU and international corporations have been eyeing up Sicily as a potential logistic hub for a while but the viability of such projects is hindered too much by the ferry bottleneck, even with other improvements to the internal rail network.
The main benefit for the city of Messina is to be freed from the slavery of ferry queues that create giant traffic jams in the whole city, but the greater economical benefits are going to be seen in cities elsewhere on the island because they have bigger ports or greater industrial hubs, or even simply more residents vying for a viable alternative to the airplane to travel to the continent.