There is wide reaching news articles about this topic, one example you can read it via google translate: https://www.cumhuriyet.com.tr/haber/marmarayin-neden-kapatil...
I believe Siemens is actively lying to cover up the corruption scandal. This will blow up hugely after the elections.
There is a press ban on the corruption scandal, all news articles have been ordered to be deleted, the article I read about the scandal has also been purged from the web, this is the tweet of the esteemed journalist who was tipped about the corruption scandal: https://twitter.com/baristerkoglu/status/1565395320296587265