> 1 tbsp of animal fat has about 900 calories.

This is extremely false. Please verify your sources better (and apply a skosh of critical thinking).

> 1 tbsp of olive oil has 135 calories.

This is false too, but at least it's in the right ballpark.

That’s not true. They have the same amount of calories roughly. It’s physically impossible for animal fat to have that many calories. Tallow has 900 calories per 100 grams while olive oil has 884. They are almost pure fat and pure fat has 9 calories per gram.