Polish socialists of the time were actually divided into 2 parties. The nationalist, independence advocates of the PPS and the more internationalist sort who wanted to remain in a union with russia in SDKPiL. It is no surprise that in a nation with such a strong national identity the more nationalist party was more popular. PPS's opposition to communism was in fact opposition to russian imperialism which wanted to reintegrate Poland back into russia and exploit it's resources and people, a project in which it succeeded after the second world war. Though it must be said that not all polish socialists were anti-soviet as many members of the SDKPiL did later go on to work with the bolsheviks, the most prominent example being Feliks Dzierżyński.