There are also European and Chinese manufacturers. E.g. Volvo already has trucks on the road and the Chinese have a huge head start for producing all kinds of electrical vehicles. So companies like Geely, BYD, etc. are also entering this space.
But you are right that Tesla is neither the only one in this market nor the first to market. They would have been five years ago when they first announced their plans. A lot of companies have started building their own trucks since then. However, product announcements are one thing and volume production is another thing. If Tesla manages to get to volume production over the next two years (like they announced), they'll still be early enough to grab a decent chunk of the market. Especially in the North American market which is pretty much wide open still. Tesla seems uniquely positioned with their supply chains to pull this off.
But you are right that Tesla is neither the only one in this market nor the first to market. They would have been five years ago when they first announced their plans. A lot of companies have started building their own trucks since then. However, product announcements are one thing and volume production is another thing. If Tesla manages to get to volume production over the next two years (like they announced), they'll still be early enough to grab a decent chunk of the market. Especially in the North American market which is pretty much wide open still. Tesla seems uniquely positioned with their supply chains to pull this off.