Juan has posted several times regarding firefighting; he's been wildly inaccurate each time. I didn't bother to watch this one.
Typically in aerial fire, mishaps involve either an impact with terrain while maneuvering (catch a wingtip, high rate of descent with inability to recover, rising terrain, etc), a mid-air collision, or a structural failure. Frequently smoke plays a part, as visibility around the fire is often hampered or very poor, and wind, other traffic, fire requirements, and other aircraft are often a factor. Turbulence is often significant.
Australia has a very stunted fire program, as opposed to countries like the US, or Canada. Once aircraft get launched to a fire, it's largely on the aircraft, with little in the way of an established communication network, dispatch coordination, command and control, or anything that's. the norm in the US. That played a part of the Coulson C130 that went down.
The best way to describe flying an approach to the fire is that you're going to take your airliner to a coordinate which may or may not be the fire, and when you get there, get local input from guys on the ground or in the air who may or may not be able to see the fire, and you're going to fly an instrument approach without LNAV or VNAV to a runway that doesn't exist in dynamic, rapidly changing unreported weather conditions, rapidly changing visibility, often in formation with dissimilar aircraft, in severe to extreme turbulence, at a heavy weight, in mountainous terrain, with no radar coverage, no air traffic control, and up to 30 or more aircraft in close proximity. You may or may not have a clear idea of the target description of location, maybe lead into the drop by another aircraft when you can only see its beacon, and if you have EGPWS, it will all be red. You may or may not be able to see your instruments because it may be too violent. Your clearance for the approach, if one is available, may be something like "target is a burning line of trees, crowning, running north south, start your drop at the rocky outcrop, run it to the road intersect, powerlines in the area, go half-in, half-out. Coverage level four, on the exit, climbing left, cleared to maneuver, cleared to drop." Or you may get nothing. You may be the only one on the fire, or you may be coordinating with a leadplane/birddog, air attack, ground incident commander, or no one. Or a helicopter. Or another tanker.
The determination on the drop direction of turn is tempered by surrounding terrain, very often smoke. There may be a steep downhill run, turning drop. It will be handflown, as will all maneuvering in the area, including instrument flying. Your drop will terminate in a missed approach, which may be climbing, but may be descending, and hopefully will terminate in losing most of your payload, usually fairly rapidly. Your aircraft will want to climb, but during the drop, the altitude of the aircraft will ideally keep a constant height on the drop line, for numerous reasons. You may have to throw out the gear for speed control on the drop. There may be corrective maneuvering on the drop run, and your actual drop will be all by feel and by eyeball, and experience; there's no instrumentation that can do that for you, and it may mean adjusting in real time to wind, fire, smoke, terrain, changes in the fireline, personnel who appear the fireline, or the appearance of other aircraft or hazards during the drop. I've had all of those things happen.
Add to that exploding trees, or like happened this last season, aircraft that are hit by trees that are falling, on fire, and exploding (happens).
A lot going on. So, why would this aircraft his the ground or impact terrain on the drop, and is it simple to determine in the absence of information? You tell me? After a lifetime of doing this for a living, I'm not as adept as Juan at ferreting out the answer. Of course, Juan has never done aerial fire, so perhaps that makes him an expert.