EasyCare "Lack of lube" Nationwide

Owned my vehicle for roughly 3 years. Driving home from work one night my car begins to fail. I then immediately exit the interstate and the coast into a gas station. The car would be towed from there. The shop takes a few days to even get to the car. They talk with EasyCare and can't find anything from basic diagnostics. EasyCare now requests that I authorize $800 top end tear down: this is just labor to find the problem. Third party is hired by EasyCare to come verify the information found by the tech at the shop. Not enough information. Now I have to authorize another $500 for the shop to split the motor. Now we can see what's wrong. This is the second time the adjuster has come to look at the vehicle.Piston shattered from high boost then motor failed. This caused oil to run through the turbo out of the exhaust. EasyCare says based off the pictures that were taken by the 3rd party adjuster they hired the conclusion is that I continued to drive the vehicle in failed state which is what caused the motor to fail. This all leads to them claiming I was driving the while their was a "lack of lube" . Keep in mind I have 3 years of scheduled oil changes and regular maintenance performed. After speaking to EasyCare on multiple occasions one of the reps told me to call the shop and have them call and give a more detailed explanation or find more evidence to show what caused the failure. Tech tells me high boost caused the failure which caused the lack of lube. EasyCare says the lack of lube happend 1st. Yet my service records indicate current oil change and mileage. At this point we are at week 4 of this whole process and they decide to cover $4,900 of a $12,000 engine replacement. This leaves me with roughly $8,700 to pay out of pocket. Not small change by any means. So my question is what makes it okay for a company to have so many fine lines to screw over the individual? Luckily I've caught them changing their own story and rewording the conlusion to fit each conversation we've had. Always leads to the shop hasn't provided enough information otherwise to prove anything different from our conclusion found in the evidence of the pictures taken of the damage by a third party company that we hire as an adjuster. This has to be resolved. I feel I have a pretty strong case and would like any help offered.