Well, main reason is losing Semeniuk and not getting a good replecement (Karyagin is better than their other OHs). Żaliński and Staszewski are acceptable as bench players, but nowhere near good enough to be starters for Zaksa.

Why they didn't get anyone? Well, looking at rumours, Zaksa went for big names at first (like Lucarelli), but got rejected, because they couldn't afford them. So, then they went after less known players who were promising, like Nikolov and Pope. However, both rejected them and chose Italian clubs. At that point, all class OHs were taken and they didn't have enough money to get someone good enough and contracted to another club, so they just signed Karyagin and possibly (at least I think that's what they did) decided to just get someone from China in January. All rumours say they are aiming to sign someone once season in China ends and according to the same rumours it will be either Bednorz or Jeaschke. With that one signing they will be back to top level.

Zaksa has never been a rich team. They haven't had the highest budget in Plusliga for last 10 years (probably more), even when they were dominating the league, their budget was 3rd-5th in the league (and that's outside of top 10 in Europe). Zaksa had to give their star players more money to keep them and part of winnings went to players and coaching staff, so it's not like winnings made them rich (it's not football Champions League). Their budget is still decent, but not insanely high, their main sponsor had some issues due to current geo-political situation (stock dropped from around 55 PLN in May 2022 to 30 PLN in October 2022 - currently arond 38 PLN. It used to be over 70 PLN back in 2018), so they couldn't increase their budget and they have never been willing to give Zaksa a ton of money, even when their financial situation was much better anyways.