It's not ignorant really!
Off the top of my head/very simplified:
Your body consumes carbs for energy by default
When there are more calories from carbs than needed for energy they're converted into fat storage (gaining weight)
When you use up more energy than is provided through ingesting calories via carbs your fat stores are broken down into energy and used up ("burning fat")
--> The above is accomplished by producing ketones, you're in "ketosis", hence the name keto diet. Not to be confused with ketoacidosis, which is when you're body can't regulate the production of ketones - this can be fatal, and is not caused by a health conscious keto diet.
If you keep your ingestion of carbs low enough to not take yourself out of keto then you'll continually produce ketones and target fat stores as your main source of energy (along with calories from fats and proteins ingested)
Essentially you're just skipping the carb breakdown pathway
It's extremely easy to lose weight on a low carb, moderate protein, high fat diet... but that doesn't mean you should ignore calories completely, especially if you're eating high calorie dairy. It's hard to get into keto and people sometimes experience "keto flu" where they're nauseous, grumpy, fatigued, etc. Some people take 24 hours to get into keto, some people take 72+. A lot of people feel much more "clear headed", energetic, motivated, and happy on a keto diet once past the "flu" stage. I don't experience flu like symptoms but I definitely crave carbs when going back into keto.
The first time I heard of keto was when a roommate of mine told me he used it to go from being an American football player to a rugby player. The results can be drastic.