Car tax

How does it work these days , apparently my mrs new car is £645 for the first year then £180 pa , why the massive amount more for the first year ? Is it to get you to buy electric ? If so why does it reduce 2 / 3 etc years
Or is the way it’s always been with new cars , first one we’ve had

Christ that’s expensive. My 20 year old gas guzzler is only 395 lol.
Can’t help with the answer as never bought a brand new car but be interested to know.

“Tax rate after first year of ownership: £645, (including £490 premium fee)”

Cars with carbon dioxide emissions of up to 165g/km face no additional cost