About 90% of Norway's 40 GW energy production (mostly hydro) is state owned. By exporting energy and thereby getting other countries to pay, the money literally goes to the norwegian people. Not directly into their bank accounts, but into their govt budgets, which they later pay less in taxes.

There are government subsidies for consumers to either have a fixed price or a price cap on electricity in Norway as a political response to the increase. This would be harder to pull off if not most of the profits from export didn’t land in the public sector (either taxes or government owned energy companies).

Washington state has the same problem to a lesser degree. California pays more for cheap Washington hydro, which causes the costs to go up for us, although I guess not as drastic as Norway since our electricity is still considered cheap.

A significant proportion of Norway's domestic energy production is hydro, which comes with it's own "built in" storage up to the capacity of the dams, so Norway already has a very significant storage capacity.

Estimates suggests a storage capacity of 87TWh of storage in hydro reservoirs, compared to production capacity in recent years between 146 and 157 TWh, and a theoretical production capacity of ~309TWh (I don't know the basis for that - I'd imagine peak production at all the plants, but I doubt that could ever happen in reality, so the 146-157TWh based on real production are better...)

Compare that to Norwegian electricity consumption of 124 TWh in 2020.

Of course, since so much of Norways total electricity production is hydro, large storage is necessary, as the hydro supply is highly seasonal, based on e.g. things like the amount of melting snow in the mountains in spring.