The reason is that no one was in a position to exploit the EV credit system because it didn't exist yet. Right place, right time, only made possible by having a bunch of money and zero qualms about exploiting that program.
Yeah. Same reason no-one is emulating Gates or Jobs right now. Their oportunity was related to their historical moment. It has passed. People will be in the right time and place for _other_ opportunities (see Zuckerberg, Bezos)