As far as I'm aware, it was purely just an odd marketing strategy and a loophole for Mitsubishi to get an extra entry into rallying.
Mainland Europe never had that model of Lancer (since the Carisma was already out and filled up the Lancer's role in that segment), so in order to make the Evo marketable, they slapped a Carisma badge on it as it was of a similar size and shape. The only real tenacious link between the two was that the facelifted Carisma had some remarkably Evo V-esque rear lights. Even though its a poor similarity, it was enough for them to be able to market it as a Carisma.
The other bonus was that as it was now a completely 'seperate' model, it meant they had met homologation criteria and could enter it into WRC events. Mitsubishi were basically running double the cars. They didn't stick at it for long though in fairness.