Oils go rancid by premature oxidation of the fat. Saturated fat is least susceptible to this, polyunsaturated oil the most. Rancid fat is quite toxic and will suppress the immune system, slow metabolism and cause other issues.
Butter and coconut oil are nearly 100% saturated fats, with 2-3% PUFA. Olive oil is a bit higher in PUFA, 8-11%, so it decomposes more easily when heated up.
Consider that olive oil is one of the most counterfeited products in the world. It is very common for producers (Greece, Italy, Macedonia etc) to add low-quality seed oils, and this is hard to detect. Research the price of olives, the amount of olives needed for one liter of olive oil, and the price olive oil sells for in supermarkets - it doesn't add up.