ICE test train reaches speeds of up to 405.0 km/h

This article communicates what this is about very poorly, so I'm not surprised a lot of people are asking "what is so special about this train?".

The answer is: Nothing. Many ICE trains have the capability to go that fast* - and some already surpassed these speeds on test tracks decades ago. It's really nothing special to make a train go these speeds.

What this test was supposed to show is that the real track (not a test track) between Erfurt and Leipzig/Halle can now support trains going that fast. Having compatible tracks is the real challenge (and cost sink) for high speed transport, not the trains themselves. Creating high speed track that is safe and usable in year-round conditions while being affordable to build and maintain is surprisingly hard.

* ICE-3s reached up to 368 km/h in tests, though ICE-4s are designed for more economical speeds in the 200-300 range and currently limited to 265km/h in software for safe operation.

It's also worth noting that ICE train does not mean internal combustion engine train, which was my second read (my first read being some super-deportation-train probably doesn't need to be clarified as even as I imagined that I knew it couldn't be right). It means "Intercity train", which a quick lookup clarifies as an express train between two cities that's longer than a commuter train but with fewer stops than your typical regional train.

Makes sense I'm not familiar with the term, as the closest match in my area is Caltrain (express trains, at least), which is still probably just commuter rail. I guess it's what CAHSR is trying to be.