/ Why communism failed in Poland?
It's not a question of communism failing in Poland; it's a question of the Polish people being ready for communism. The backwardness of the peasants, the Western-looking intellectuals, the demoralized urban classes, the destroyed infrastructure spelled the defeat of that system before it could even take root. The social conditions were not right for communism in Poland.
When Marx spoke of communism he meant it for the developed, industrial nations like France and England. It was never his aim to advocate it for peasant societies like Russia or Cuba. It is, however, in those societies that capitalist oppression was more easily seen. For Marx, however, a society had to undergo capitalist development before it could arrive at socialism. It's interesting that his socio-historical insights are accurate in that regard (all of those countries that wanted to skip this stage of development are now forced to go back to it).
Of course the way the Bolsheviks went about it was all wrong. They actually defeated workers' uprisings and forced the Soviets (the real revolutionary organs of participatory democracy and economic planning to submit to the state). Lenin's NEP actually allowed for some private enterprise. There were many communist revolutionaries who were disappointed with such arrangements, calling Russia a state capitalist country.
So, did Poland even really experience something like communism? This is another question. It's worth pointing out that the USSR called itself two things: socialist and democratic. The latter claim was always contested by Western intellectuals, but not the former. Why? There is enough literature to suggest that Russia was not a communist society by communist standards, but it is a good propaganda tool to be able to point to the USSR and say, 'that's communism.'