A key component of this bill is that the rebate is instant, applied automatically when you purchase the vehicle. California currently has a mail-in EV rebate program for certain car models, but purchasers have to wait up to 90 days to receive their funds. It's possible that this wait makes people less likely to choose electric over gasoline power for their vehicle.
While it's not clear exactly how much each rebate would be, The California Electric Vehicle Initiative would be income based. The state is specifically concerned with helping low-income residents purchase EVs. Their goal is to bring the purchase price of electric cars down to their gasoline-powered equivalents. The bill currently proposes putting aside around $3 billion total for these incentives.
The legislation hasn't been passed yet; while it passed an assembly vote, it still needs to face two Senate committees. It's notable, though, because California is often a leader in emissions and car regulations for the rest of the country. If this becomes law in California, it's possible we could see other states following suit.