The Whites were the victors, but they seemed to pretty quickly bring the Reds back into the political process. Why was this? Did they need the Reds?
Similarly, why were the Reds open to reconciliation, particularly after the 'White Terror'?
What part did outside forces play, such as the situation in Russia and Germany?
Sources for further study would be much appreciated. I'd prefer English or Swedish, if available, but I can work my way through Finnish texts as well.
A lot of that has to do with the actions of Vaino Tanner after the civil war. He managed to get a move the left wing SDP party in a less radical direction. He then expelled the more radical elements from the party and these groups then splintered either joining the communist party or the SSTP. In this way the SDP was purged of members calling for outright revolution, the fact Tanner stayed Neutral during the civil war probably also aided the rehabilitation of the left wing party.
The nature of the Parliament, which often featured minority government probably also played a role, sometimes through working with other parties (often the Swedish speaking SFP party) were able to pardon several prisoners from the civil war as well as get some socialist policies passed.
The defining moment probably came when Tanner of the SDP was allowed and able to form a minority government in 1926, which resulted in non of the worst fears/predictions of some on the right coming true.
Most of that is taken from Eino Jutikkala's section of the book History of Finland. He has other works but most of his lectures are in Finnish.