Why is it suddenly so difficult to drive trains?

The recent spate of train crashes (the D.C. Metro crash being the latest, but the green line T crash in Boston also fresh in my mind) leaves me asking, why is it suddenly so difficult to drive trains? It seems like there's been an uptick in recent years, despite systems that have been in place for years and have far less hazards than, say, coordinating airplanes. And it makes me question my recent post about why we can't go back to more train travel.

Photos of the D.C. crash