I didn't see this covered on the forum yet, and hopefully this isn't a duplicate.
Two new high speed rail routes between Italy and Germany will be implemented next summer, one from Milan to Munich and one from Rome to Munich - https://www.timeout.com/news/two-new-high-speed-train-routes-coming-to-europe-milan-munich-rome-090326 . I imagine these will reduce at least some of the budget air flights.
Even though the rail travel time may be slightly longer than air travel, I would still prefer the train as I find it to be a much more pleasant experience.