It ought to be a lot simpler to engineer driverless trains than it is to do driverless cars or trucks that are currently all the rage.
Simpler? Yup. Simple? No. They've been working on this for years - well over a decade. Various PTC solutions are being rolled out. I don't know much about the system Amtrak uses but I have worked on other PTC solutions. It's incredibly difficult to get right. For one thing, you essentially have to get FRA approval for the way you've handled each mile of track.
But if you notice almost all the deadly train crashes in recent years come down to drivers not paying attention and going too fast or running into other trains. This is a solvable problem, one that is in the process of being solved. There are a lot of people who will be looking at this incident and determining if the current solutions could have prevented it, believe me.