The EU, Soros and NGOs ran another color revolution in Poland and they won.
A coalition of three left-wing parties has over 52% of the votes according to current results, which means the conservative government is history.
Expect Poland to go all in on the EU and to open the migrant floodgates, leaving Hungary as the last man standing.
It could also just be typical incumbent fatigue. When a party is in power for a long period in any "democracy," voters tend to turn against them even if they've governed well. Even some of their supporters will stay home instead of voting for them again, either due to discontent or complacency. It's too early for reliable turnout numbers, so I don't know how much of a role this has played.
There is also the possibility that the elections have been covertly Soros'd.