I believe the fact that Polish uses the Latin alphabet (with a small Slavic twist to express the extra sounds) meant it was much easier for Poland to align itself westward. I think the average Pole is much closer culturally to the Western neighbours than to a Ukrainian or Russian (maybe apart from cuisine).
Like Kazakhstan, which decided to switch from Cyrillic to the Latin alphabet [1] in order to align more with Europe and less with Russia.
I wonder if Ukraine will do the same in a distant future...
[1] https://www.bbc.com/worklife/article/20180424-the-cost-of-ch...
Being Catholic helps too
Polish cuisine is very similar to German cuisine.
(This comment will make a lot of Polish people very upset.)
The adoption of the Latin alphabet was itself a move to align itself westward, with kingdoms in the Latin world, not the Byzantine one, and tied to adopting Catholicism rather than Orthodoxy.