They don't make more profit per vehicle, they just made more profit in a short window of time by doing more sales but this may not be sustainable because it just shifts sales around rather in time at a lower profit per vehicle.

Production bottlenecks.

Tesla is constantly behind on producing cars for its customers. They just wanted to generate money now rather than later.

Building lots of cars is hard. It takes a lot of time and money to ramp up production capacity to this level. They've been building cars as fast as they could for years now.