Dave Meltzer explained on today's Wrestling Observer Radio as to why New Orleans was awarded WrestleMania for the second time in four years. He said that there 15 Cities in the running to host WrestleMania 34 such as Philadelphia and St Louis but ultimately New Orleans put in the highest bid for the event. It's not entirely based on what stadiums the state has.
Senior officials in New Orleans pitched to WWE that Wrestlemania would be treated as a big part of New Orleans and it's history given the state will celebrate it's 300th founding anniversary in 2018.
The decision to award WrestleMania to New Orleans was made in the last few weeks.