The incentives are to encourage adoption, if that happened, they should go away. As for the increased registration it needs to both offset the gas taxes and account for increased road damage.
One of the sponsors of the bill (that increased the EV registration fee in order to fund roads) is a state senator who is also the COO of a major roadwork construction company.
He's also simultaneously the mayor of a 10,000 population town with only a couple public chargers. Way more trucks than EVs in his town btw.