Unfortunately, the ground was soft grassy area"
This is typical of your problem. You have measurements on how soft this area was? What is the soil strength profile here? You certainly cannot tell from a picture. (and yes, I am an expert on this subject).
That's what the problem I have with the "expert" opinions on the PM article. As an expert giving opinions to popular mechanics, without pointing out at the crash site how hard was the soil, how much kinetic engergy was absorbed, and how much deflected because of the hardness of the ground, resulting to, for example a 10 yard bounc up and 300 yard traveling, it doesn't have to be acurate, but reasonable, I would buy it. Simplly saying bounce up from the ground because the speed, makes me think: hello Mr. Expert, who are you trying to fool?
A large, but not solid, collection of metal objects weighing in the hundreds of thousands of pounds impacts the ground at 500 mph and a piece weighing a few hundred pounds travels 300 feet in the direction of impact. Sorry that is just not a big deal.
The point is valid, engine core is not a solid piece, however the kinetic engergy per pound is going to be the same for a bullet or an engine.
A car has the almost same weight as an 757 engine, imagine if it travels 500mph and headon to something solid.
As an expert, you should know that the 300 feet doesn't matter, the speed on impact and the mass of the object provide the kinetic engery. By the time it hit the ground, the potential engergy has already transfered into the speed, become kinetic energy.
If the ground is solid, is the engine core designed to withstand a 500mph 2 ton kinetic engergy, without shattering into pieces? These all can be calculated with physics and engineering, I can not be convince until I see some reasonable figures. Again, it doesn't have to be rocket science accurate, but reasonable, I believe all techies accept a set of reasonable figures, alone with some educated speculations.
A fan, falling by itself, happened to hit the ground flat (the chance was very small), the larger area will create less presure (psi) on the soil, might bounce up and roll down the hill, if the soil is hard enough, but you have to do some calculation to convince me. Not "For something to hit the ground with that kind of energy, it would only take a few seconds to bounce up and travel 300 yards." That's worse than the conspiracy theory and speculations, because it came from a so called expert. It is even scary to me. How serious are they? We are talking not about a stupid engine or a fan, many lifes were lost.
If they found a fan, where was the engine?