I have some light olive oil in the fridge that did not get clumpy at all. Maybe oils with a certain property?

Why did the extra virgin oil clump so strangely, rather than, say, bacon fat which solidifies evenly?

Interesting fact: safflower oil is the only type of oil that does NOT get clumpy like this when refrigerated.

It's fine. it's the veggie fats in the oil cooling.
Just bring it to room temp to use.
It's a good way to store oil that you don't use often, like walnut oils, sesame oils, almond oils etc. Because it keeps them from becoming rancid.

As for olive oil.That's never a problem around here as that gets used up far quicker than it can loose flavor.