I hope everyone who was involved in the crash recovers well. Incidents like this are always horrible to deal with.
There's not really enough information on why it happened as of yet, so I don't really want to make direct conclusions. By the looks of it, could be a combination of issues from both the manufacturer and the amount of maintenance M&D gave the ride, but in till we have a conclusive report on what went wrong, it could be many different things.
It's sad to think that the media in the UK have jumped on this again and used it as excuse to fear monger and bring up the Smiler incident again. This was an incident on a small, fairground-type rollercoaster, and should never be compared to that of larger theme parks.