There may be several reasons.
Finland may be less reliant on Russian energy imports being way, way north of Europe's main oil and LNG ports and the pipeline terminals from Russia to the west. For historical reasons, the Finns also distrust, in many cases hate, Russia, and they have very good cause to distrust and fear the current regime in Moscow. So, I wouldn't be at all surprised if Finland deliberately avoided reliance on Russian energy supplies unlike most of the rest of Europe, especially Germany. It may also be far more energy self-reliant than the rest of Europe - there are some Finns on the forum, and they'll no doubt know.
Second, Vihtavuori appears to still have production capacity to serve the handloading and sporting cartridge markets despite the continent-wide increase in military demand . Alliant on the other hand receives its powders from Eurenco Bofors in Sweden, and Nitrochemie Wimmis in Switzerland, the latter half owned by the huge German/Swiss RUAG combine which makes most of Europe's military ammunition (as well as GECO and RWS sporting brands). Both of these powder companies are working flat out on military orders and powder supplies from both have virtually dried up to other customers, just dribs and drabs appearing, presumably to keep their distribution and sales networks and brand awareness barely alive. (This also applies to Norma brand powder grades which are 100% Bofors manufactured.) The resulting ammunition outputs are by no means all going to Ukraine - many European nations are finally building up weapons and ammunition stocks thanks to the Russian threat. Much is being soaked up by a huge expansion by the Swedish military and Bofors/Norma are Swedish companies even if part of European multinationals.
Finally, with capacity still available, Viht may have taken a marketing decision to ramp up production to the maximum, but keep prices down in order to build market share. If they have, they are being very wise IMHO. Other makes are seeing their brand reputations, dealer networks, market shares destroyed. (Isn't that what this topic is about, ie saying I've used Alliant grades for years, but won't be going back to them even when things improve?) Viht has a golden opportunity here to win a large share of the world's largest shooting market the USA, especially after its parent company's (Nammo) substantial investment in the USA pre-Ukraine in Berger and (finally!) a comprehensive and apparently efficient marketing, distribution and sales organisation in the form of Capstone Precision with a new purpose built computer, warehousing and distribution facility in Minnesota.