The "bump" that occurred a few months ago & this one sound more like a software or operator error, not a lack of maintenance.
Making sure the software operates properly is a maintenance issue. Just ask any of the technical people who keep this website operational. It may not be maintained by the same person responsible for the nuts and bolts, but it is maintained by someone.
When the 2nd accident happened, and the flaw which allowed the two trains to occupy the same zone was discovered, one would think that the software system would have been given a hard look. After the 2nd accident, those involved said that the safety system would not allow occupied trains to enter the same zone. That turned out to not be the case. Disneyland has a responsibilty to make sure that a ride's safety system does what it is supposed to do.
The severity of the the injuries, is not what makes these accidents serious. It's the failure of the redundancy safety system. What's the point of having one if it can't be counted on to work? A well designed and run ride system is going to call on the backup safety system infrequently. Two failures of the redundancy system seems to indicate a high rate of failure, and one has to wonder is this the only time that the backup system will fail? And what about the backup systems on other rides?
Oh and the Matterhorn. About 10 years ago, they determined that the mountain structure was reaching the end of its life. They had a choice to tear down the whole thing and rebuild, or replace sections at a time. A far more costly and time consuming approach. Disneyland chose the latter (this was pre-Pressler). The reason the Matterhorn goes down every off season is to do the replacement. The track, the supports, the skin, it's all being replaced. It's not a case of deferred maintence catching up, it's about the only completely planned maintence project in the park. At least until Ouimet came in.