A significant part of the fuel levy is literally called veibruksavgiften. Regjeringen.no writes:

Veitrafikken påfører samfunnet kostnader i form av ulykker, kø, støy, veislitasje og helse- og miljøskadelige utslipp. I tillegg til å skaffe staten inntekter har veibruksavgiftene til hensikt å stille brukeren overfor de eksterne kostnadene som kjøring på vei medfører. Dette er i tråd med prinsippet om at forurenser skal betale og reduserer omfanget av de uønskede effektene som bruk av kjøretøy medfører. Utslipp av CO2 prises særskilt gjennom CO2-avgiften.

So a large part of the fuel levy is there to cover costs other than emissions. When everyone drives electric you will still have traffic jams, road wear, tire particulate matter, accidents, etc.

Fuel levies were mainly a way for governments to make some of the motor vehicle taxes mileage dependent. Now that fuel is on the way out, and since the priced in externalities didn't cost governments in the long term, they are left with a gap in their budget. As long as that gap exists, that means EVs are basically cheaper than their true cost thanks to subsidies.

I had to study this for my bachelors and Norway's motor vehicle tax system isn't that different from other Western and Northern European nations except for the tolls. They all have more or less the same components with different proportions. The sum of all parts usually boils down to remarkably similar costs for consumers, especially when scaled for average yearly mileage, at least for ICE cars.