This is personal and professional. My wife and I have the third edition of our comparative economics textbook now in press at MIT Press. We have chapters on transition economies, and one is on the Polish economy. The standard story is that Poland has been the great success story of transition (now accepted to be over pretty much everywhere for awhile now). It adopted largely western market capitalist institutions successfully, while avoiding mistakes made by other transition economies. It avoided dismantling its social safety net. It was careful about privatizing state-owned enterprises, and in fact continues to have a higher percentage of its output run by them compared to most other such economies, with this tied to its lower rate of corruption than many of them. While it joined the EU, it avoided giving up its currency, which allowed it to devalue and preserve economic growth even as EU nations fell into recession.
Indeed, the ultimate economic success of Poland came during the Great Recession when it was the only nation that did not go into recession at all, steadily growing even through the pit of 2009. It was the first Soviet bloc transition nation to come out of its transition recession, with a reasonably functioning parliamentary democracy, and it has outperformed all the rest economically. In 2007, its president, Lech Kaczynski of the conservative Law and Justice Party, signed the Lisbon Treaty, which allows the EU to enforce judicial independence and other features of western democracy. Later he would die in a plane crash in Russia, which led to his twin brother, the party's current leader to formulate conspiracy theories that Russia was behind the crash. A souring of attitudes came over the party as it went into a period out of power. But Poland would become one of the most respected members of the EU, with a former president, Donald Tusk, now an EU leader.
On returning to power the Law and Justice party has followed a new track, obsessed by conspiracy theories, it has turned against Russians, Muslims, and Jews, but loves Donald Trump as well as the also neo-authoritarian regime of Victor Orban in Hungary (who is pro-Russia in contrast with the Poles). Both now thumb their noses at the EU and its rules. The latest for Poland is a new law that allows the government to remove half the judges and otherwise take firm control of the judicial system in a way violating Section 7 of the Lisbon Treaty. The EU has formally condemned this move under the treaty, with tis setting up a possible loss of voting rights in the EU for Poland. But the government seems not to care and is more committed to pursuing its nationalistic and authoritarian policies.
An irony of the current situation is that one of the politicians driving the changes. Stanislaw Piotrowicz, was a prosecutor during the period of Communist rule prior to 1989 who helped put dissidents in jail. The irony here is the extreme anti-communism of the Law and Justice party.
What is mysterious is that there is not some obvious economic crisis or problem that is driving this "populist" political trend. Again, economic inequality is not high and corruption is low. The unemployment rate could be lower, but the economy has seen much growth reasonably well distributed, and it is broadly stable without inflation or major control by foreigners, even the hated German neighbors.
That said, one subtle issue of economics may be playing into this, even if it still seems to be secondary. Moving out of the Soviet bloc into the EU has changed the frame of reference. Whereas preciously the Poles could see themselves as better off economically than the politically dominating Soviets. Now they compare themselves to higher income Germany, France, and the UK. Indeed, an irony of the UK Brexit movement is that a motivating element in it has been anger over immigrant "Polish plumbers" supposedly undercutting good local Brits in the job market. The Poles are going elsewhere than Poland to better themselves economically, and this may well provide a backdrop that supports the current dark political trend.