Back when Tesla was the only long-range EV you could buy, well, Tesla pretty much had the market cornered. Now, with other manufacturers offering long range EVs, Tesla just isn't standing up to the competition.
Here are some non-political reasons why, IMO, Tesla sales are down:
1: They do not justify the price premium, because they do not feel like a luxury vehicle. The interior is basically a mass market vehicle with pleather. (And the Cybertruck is just too expensive.)
1a: They severely dropped the price of the Model Y right after people bought it, with no goodwill. (This happened to me.) Ford dropped the price of the Mustang Mach E shortly after, and then offered goodwill to people who recently purchased it.
2: They have weird quirks:
2a: The yoke (square) steering wheel in the Model S should have always been optional.
2b: The automatic windshield wipers work very poorly, and there is no wiper speed control on the stalk. The "just push the button and spin the dial on the steering wheel" is not a solution. (Either use the same kind of sensor that other car manufacturers use, or bring back the old fashioned dial on a stalk.)
2b: The heat/AC and radio turn on when you open the door. (I hate this.)
2c: On newer Teslas, shifting happens on the touchscreen instead of a physical shifter.
2d: The general lack of physical buttons. The car doesn't need a button for everything, but even some programmable physical buttons would be a huge improvement.
3: The Model 3's driver's seat is too uncomfortable. (The Model Y's driver seat is better.)
4: They should have a wider range of vehicles by now. For example, they should have a Cyber SUV based on the same platform as the Cybertruck, but with 3 rows. They also need to have a lower-end vehicle.
5: They can't "ship." They've had pre-orders for the roadster forever. In contrast, Chinese EV makers come out with new models much faster.
6: They are sorely behind on Autopilot. Other manufacturers allow hands-free. The promise of full-self-driving was never met, people who paid for full-self-driving in their 2018 Model 3s will never get a true hands-free self-driving car while they own it.