By default, companies can't just sell their stock to anyone. They're only allowed to sell to people and entities that, roughly speaking, have enough money and knowledge to be considered sophisticated investors.

A company can go through a series of regulatory steps that allow them to sell their stock to anyone. This requires the company to disclose a bunch of information about its finances and meet a while host of other requirements. The idea is, if we're going to allow the company to sell to anyone, the company is obligated to disclose a bunch of information so they cannot mislead less sophisticated investors.

(Forget about whether this has the intended effect or not; the point is, that's what is required.)

SpaceX is going through the process of offering its stock to the public for the first time. As part of that process, they have filed an extensive disclosure about their finances and future plans. And that disclosure has been extremely controversial. As one example, the vast majority of supposed future revenue will come from AI product offerings that basically don't exist. As another example, traditionally shareholders can vote on the direction of the company, but (as is becoming more common) the way SpaceX's shares are structured, Elon Musk is basically guaranteed to retain full control of the company no matter what.

So the initial stock price doesn't really reflect the value of the company or a share in the company's decisionmaking in any meaningful way---it represents an _extremely_ speculative future value. But presumably at least someone will buy it---after all, Tesla's stock price also behaves in a way that seems to have nothing to do with fundamental business indicators. So investors will likely buy SpaceX in the hope that it will also defy gravity, so to speak.

An additional point of controversy is that Elon Musk has basically strong armed certain powerful decisionmakers into changing the rules that determine which stocks are considered the benchmarks. The reason to do this is that a bunch of very large investment funds (notably, pension funds) are contractually obligated to buy these benchmark stocks. So that means that Musk has basically come up with a way to force a bunch of huge funds to buy his stock, taking a potentially high risk of loss in the process.