Are coronavirus victims dying from dehydration ?

No.  They are dying from organ failure after their lungs are unable to process enough oxygen to keep those organs (like kidneys) functioning.  

Once the lungs are filled with fluid and unable to function, even when aided by a ventilator, they vital organs begin to shut down due to lack of oxygen in the blood.

No...................

No. they are dying from respiratory distress/collapse

No. Inabilty to breath properly due to dammage to inner lung structures