Liberum veto abuse was a symptom, not the cause. The practice existed since forever, but before late 17th century it was only used to block a particular issue, not the whole session, and only temporarily. And it was OK.
Then in one case it was abused (technically correctly) to veto a movement to lenghten the parliament session because consensus wasn't achieved. One guy vetoed that, and sejm was finished without any decisions.
Then it started to be abused illegally to finish any sejm completely at any time (even 1 day into the session which were supposed to last weeks) when even 1 nobleman vetoed. It wasn't the problem of the law, because it was illegal to do so - it was the problem of the implementation of the law - because influential people wanted it to be abused that way.
But the real reason was - Poland lost several important international struggles (over Baltics vs Sweden and over part of Ukraine vs Russia), and international economic situation changed (agricultural revolution started, decreasing grain prices on the western markets). Additionally after series of barely survived wars Poland lost a lot of population, so the grain production decreased (and it was like 99% of Polish economy).
Becausse of all of that - infulential people in Poland perceived Polish interests as unrealistic, and alligned themselves with more profitable groups - Prussia, Germany, Catholic Church. And to further their cause they were breaking the law by abusing liberum veto among others.
There were also patriots, of course, and they broke the law, too (3rd May Constitution was introduced in a coup supported by Prussia basically). But in the end Poland was already a Russian protectorate, and there was no way to fix that as long as Russia was so much stronger. Only after WW1 it became possible.