When tomatoes are fried, you can see that the oil becomes coloured red - so at least some of the colour components are preferentially soluble in oil.
I will hazard a guess that, under the circumstances mentioned, the oil coats the tomato particles, and some of the colour migrates into it to give a red surface. Because the oil forms a coating, that coat will inhibit oxidation. The oil will also improve the mouth feel of the soup.
Just the way I see it ...
Yes, your pan was too hot.
Because your pan was empty when you heated it, it had minimal heat capacity, and could only lose heat by convection and radiation. Thus, it heated up quickly, and likely reached a much higher temperature than it normally could with food in it.
When you heat a pan with food in it, some of the heat is transferred to the food, and much of that heat is, in turn, lost when water in the food evaporates. This slows down the heating rate, and significantly reduces the peak temperature reached.
(Evaporating water is an extremely efficient method of heat transfer, especially at high temperatures, and even solid foods like meat and vegetables still contain quite a bit of water. Any time you put something on a hot pan and it steams or sizzles, that's the sign of water evaporating.)
Also, because you didn't have any oil or water or food on the pan, you had no easy way to gauge its temperature by eye. Normally, if you heat a pan with oil already in it, you can tell when it's hot enough just by looking at how the oil behaves. If you miss all the subtler signs, like the oil turning more runny and starting to form convection patterns, the point where it starts to change color and smoke is an unmistakable sign that you've definitely heated it too far.
With a dry pan, it's quite hard to tell just how hot it is. One trick I sometimes use is to sprinkle a few drops of water onto the pan and seeing how quickly it evaporates. (Don't do this if the pan already has oil in it!) When the drops evaporate all but instantly (but still briefly wet the surface, rather than exploding on contact or hovering over it), it's time to add the oil / butter.
Of course, the modern high-tech alternative would be to get an IR thermometer. I actually do have one, but I rarely use it — it's just quicker and easier to dip my fingers in some water and sprinkle it on the pan than to get the thermometer out of the cupboard.
Best Answer
Many of the ideas we learn in highschool are in principle true, but only apply to a tiny, tidy portion of the world that is not representative of stuff we are going to encounter every day. One such idea is that substances have a melting point and a boiling point - in reality, some of them do and some don't.
Oil is made of big organic molecules, containing long carbon chains*. Unlike anorganic substances with small molecules (like water), heating oil does not lead to a point where the molecules stop attracting each other (that would be the boiling point). Instead, the big, fragile molecules just break up. Which means that oil has no boiling point at all, and it is impossible to produce oil in a gas phase. (You can produce something similar to "oil vapor" with a mister, but this consists of tiny droplets of liquid oil, not a real gas).
As oil breaks up before it boils, there is no oil evaporation. You can destroy oil by heating it, because it will turn into something different than oil. You can also burn it by heating it in the presence of oxygen, and this is what happens when you see smoke coming from your pan. (This is chemically different from simple breaking up of molecules). But no, it does not evaporate.
The chambers of the chimney get a greasy film because: 1) the particles in the smoke from smoking oil can feel somewhat greasy (pure soot feels greasy too) 2) when your oil breaks down under heat, some of the new molecules (pieces of oil molecules) can be light enough to become air borne and go up and build a film. While technically not an edible oil any more, they can have a greasy feeling to them. 3) When you fry, oil droplets fly through the air. You notice it on the stove around your pan, but I bet some droplets are small enough to be carried by the upward draft of hot air into the chimney.
*I simplified here a bit, because the oils we cook with are not made from a single chemical compound, they are a mix of different compounds. But the explanation still works for the mix, because it is always the same type of compound.