What are they building the train first?
It's summer, which means they're doing maintenance work while "everyone" is on vacation and therefore not at all inconvenienced by having to take the hot, stuffy, poorly-ventilated bus replacement service instead of the train during the hottest months. And as with most maintenance, you want to close off every parallel track on the nearly 40-kilometer stretch so that no trains at all can run on any track for that entire distance. With such a tall order, you obviously need enough time to get all the maintenance work done, so it's completely closed for about one and a half months.
Also the listed bus departure times on the website, app, and ticket machines are all wrong, and you basically just have to be there standing in line and hope you're not getting the one "funky" bus which takes an hour and a half instead of just 50 minutes to get you into the capital.
Current reports indicate that they'll need to keep doing this every summer for the next 10 years in order to get everything properly ship-shape.
EDIT: Current time: 23:29. Bus to the airport for Poland flight is at 3:47 AM. Had a few beers already, having gone out to the usual pub some time around 22:00.
Q: Go out to different pub to get even more sloshed for Poland flight? y/y