So, how do they lubricate it?
Lubrication in fuel vs lubrication using a separate system and 2-stroke vs 4-stroke are two entirely separate engineering decisions, that are in no way tied to each other. It's just that the most common types of 2-stroke engine use lubricant oil mixed in fuel, and the most common types of 4-stroke engines don't, and so they concepts are thought to be related to each other by most people who don't know much about engines.
2-stroke engines also have great power densities (at the cost of fuel efficiency), which means those two often go hand-in-hand.
Large, or perhaps huge would be a better adjective, 2-stroke diesels are extremely efficient, better than 2-stroke gasoline, 4-stroke gasoline, and 4-stroke diesels:
https://en.wikipedia.org/wiki/Brake-specific_fuel_consumptio...