Elaborating on the part i mention before about polish education:

Poland and Polish nationality basically entire existence was formatted by the partitions. Not only country was occupied and divided, but also opressed. In Prussia/Germany the oppression was strongest, polish culture and language was systemically eradicated. In Austria, it was mildly tolerated, or at least as much as Austrian regime tolerated any not compliant ethnicity. In Russia it’s the middle, oppresion was lesser as in Prussia and not consistently enacted. Partitions explain the insanely high Polish nationalism too, also the romanticism literature hit Poles very hard and is flattening the brains here ever since.

So fast forward to 1918 and the only places where Polish inteligentsia was present in sufficient numbers to actually try to assmble the university cadres and education system were the locations of current (Kraków i Cieszyn in former Austrian part.) and former (Wilno and Lwów in former Russian part.) universities, and those are lava-hot beds of nationalism, full of Mickiewicz-maniacs* very much influenced by backward ideas like romanticism and catholicism. And those cadres taught the future ones - which is also one of the main reasons of the Polish culture high uniformity noticed by many foreigners even now.

*Also note that in 1968, when the banana youth and other liberal students rioted against the socialism, the direct spark for that was also the withdrawing of the Mickiewicz play from the theatre - people organising that protest were later the core of worst polish liberalism - Michnik, Kuroń et cons.