In essentially every case outside of a rounding error, most people within a given company (or society) derive their income from selling their labour on the job market. This makes them workers, and thus they share a common material interest with each other. A very small minority of people in a company (and society) instead derive the primary portion of their income through the speculation of their capital. Their material interest is contrary to that of the workers, since they would profit from less stringent labour laws and cheaper wages, and vice versa.
Even if we consider pathalogical cases such as a blue-chip stock like TSLA that has become the focus of brief and anomalous phenomenon of retail trading, the magnitude of capital invested by retail traders into publicly traded companies is negligible, relative to the economic influence of traditional investors such as hedgefunds, and other whales in finance.
And even still, retail shareholders by definition engage in the economy primarily by selling their labour. That is how they generate the income required to put food on the table. Therefore they are still primarily workers and thus share the same material interest as other workers, as opposed to shareholders.
Therefore in every case we can say that the claim
>Tesla shareholders almost certainly outnumber its employees
is a misleading one, in this context.