A combination of both. The Polish Sejm in the 18th Century was an extremly inefficient system as any member could veto any bill with just 1 vote. Essentially all it took was the Russians paying off a single member to create a destructive deadlock that allowed for the partitions. The Poles also did try to fight off the Russians in 1792 but failed due to the shear scale of the Russian Army that outmatched them in almost every single way. They tried again in the Kościuszko rising in 1794 which was put down. Then the most successful rising in 1807 created the Duchy of Warsaw which was basically a Napoleonic puppet state.