https://pl.wikipedia.org/wiki/Maciej_Zalewski_(filolog)
He warned Bagsik and co. (who stole millions of public money through the famous Art-B company and escaped to Israel) that the police wants to imprison them - so they managed to escape. Bagsik later confirmed that they shared some of that money with Porozumienie Centrum's business named Telegraf. Somehow only the less important guy (Zalewski) went to jail, but Kaczyński brothers weren't prosecuted.
But there's a lot of low level corruption that is exposed, it's just usually ignored by country-wide media, because that corruption is local. For one example: https://samorzad.pap.pl/kategoria/prawo/prawomocny-wyrok-byl...
Is there any indicator they should have been in this case?
1. train manufacturer bricking trains - malice and monopolism as you say
2. prosecutors failing to bring court cases and convictions for train manufacturers - incompetence or more likely corruption.