I can attest to the safety systems - when opened, the Wonderland rapids ride (an intamin model) had guard towers installed all around the course, fitted with loudspeakers and staffed by ride operators who could tell riders to sit down, and to contact the control room if an incident occurred.
Later, and with improvements in technology, the ride was retrofitted with surveillance cameras that covered every inch of the ride, and could be monitored by one operator, while other staff assisted with loading and unloading. On quiet days, the operator manning the control panel could also control load and unload. the automation built into the ride by then was huge. The control logic that operated the conveyor belt and loading gates was failsafe. Sensors were mounted along the conveyor to track the location of the rafts, and more sensors in the unload and load area ensured raft separation. The conveyor stopped and started based on the ride control logic, rather than running full speed all day.
So - the absence of lifeguards around the course does not mean it was unsafe, although I don't know enough about this specific installation to guarantee the camera and logic systems were adequate, i'm just offering the fact that there may have been a very reasonable explanation for the absence of physical lifeguards.
It's ok - it was made private because they sold it to news outlets so you can now view it on any of a number of news outlets websites and social pages. It was a little disturbing with audio, without it, there isn't much graphic about it except for an upturned raft - so if you want to see for yourself how it looked post-flip, but don't want to be disturbed, turn off the sound.
After reading all i've read on this incident and now seeing the footage, it's down to one of two causes (IN MY OPINION) - either the bladder was underinflated, and caused it to snag and somehow flip, OR someone was playing silly buggers in the raft, potentially stood up and overbalanced the raft at a key tipping point on the ride. I'm not casting blame on the park or the riders, i'm just saying in my opinion these are the two possibilities.
Given the ride had been closed for months, and it had only just had an inspection the day prior, and just reopened, if it was down to inflation, my guess is the rafts were all pressured up, the inspection checked, and a slow leak lead to the deflation post-inspection. It's unlikely a slow leak would have been detected that quickly.
I do recall in the dreamworld inquest that leaking tubes were discussed, and it was a case of reinflating each day to correct pressures to keep them 'normal' - but that takes daily inspections to know which ones need to be watched - and since this was the first day reopening, maintenance probably hadn't yet identified rafts were leaking...
I feel its a lot about reopening parks that haven't operated for some time, without rigorously and thoroughly ensuring that everything is in A1 condition because (at least in some areas) nobody has ever shut down the parks for this long before