There are quite a few factors that go with this. For one, Disney isn't known for thrill rides and roller coasters. Those attractions tend to bring on more injuries and illnesses. Disney attractions tend to be more tame. Another factor is the ride systems have many safety features whether there are sensors, cameras, indicators, checkpoints, etc that detect problems and in some cases automatically stop themselves. A good number of attractions at Disney have "intrusion systems" which detect if a guest or cast member are where they are not supposed to be either exploring the attraction or jumping out. Other systems space vehicles out automatically or stop motion if a restraint sensor or abnormality is found. One of the last major factors is training. Cast members are nearly drilled to death over safety procedures. Cast are trained extensively at attractions to know how they operate and how to respond to specific situations. Each attraction has a very detailed checklist that is used when opening in the morning. Everything is checked from restraints to emergency stops to making sure signage is in place, supplies are ready, and facilities are in good condition. Cast members are audited every year on how they would respond to general situations at their locations from what to do if they experience something out of the ordinary to locating the nearest automatic external defibrillator if needed. Speaking of AED machines, Disney is the best place to have a heart attack in the world due to the number of quickly accessible AED machines that could save a life during and after a heart attack. Other parks do have aspects of these but not to the extent that Disney does.
You basic attraction cast member should know how to operate the attraction, how to stop the attraction under certain conditions, how to handle an emergency, how to respond if a guest jumps out of their vehicle, if their is a fire, if there is a technical difficulty, if the park was being evacuated, if there was severe weather, if there was a medical emergency, if there is a loss of power, or if there was a security threat or issue. To what level do you think the average ride operator at a competitor or local park has this level of training, how in depth was it discussed, and would they succeed in following procedure if thrown into this situation.
First hand, I have experienced being at a Six Flags park during a tornado warning requiring us to seek shelter. The employee didn't know where to go, communication was inconsistant throughout the park through all lines of business, and guests were very confused. Luckily I video taped it and sent it to Six Flags in hopes that it was a fluke or an eye opener. Sure there were emergency procedures in place, but did their employees know those procedures.
Looking back at situations at Disney, someone around always knew what to do to a good extent even if they were not entirely sure, were uncomfortable, or somewhat nervous about what was happening.
Of course all this said, accidents do happen everywhere and sometimes they are truly accidents. Companies and manufacturers learn from mistakes and accidents though whether it is through signage, training, procedures, or physical changes. No park, even Disney, are immune to them. The accidents at Six Flags over Texas and Cedar Point probably could have happened anywhere.
