I think it's mostly because these price increases are happening at the same time as the publishers are raking in record profits. It also doesn't help that a lot of the games seeing the increase are subpar cash grabs.
I don't see any problems with charging more than $60 for a game as long as the game is worth what they're asking. I bought Metaphor Refantazio and TotK at a full $70 and felt both were worth that (screw Nintendo, but the game's really good).
Development costs have increased drastically in the past couple decades, and while the customer base has also increased quite a bit, I think the market is reaching saturation.
I think that while greed is the most common reason for the increase, there are some legitimate reasons people should take into account before denouncing every price increase.
They say in the post they use Debian. The game is running under proton/wine and reports the is as windows.