It's probably stuff being less "indie" than it appears on the surface. Both of those games you listed appear to have successful publishers, one behind Maplestory and multi-million (in USD) net income (also largest shareholder is investment firm, Maplestory NFTs). The other has more games (and significantly more DLC) on Steam.

That doesn't really answer your question, well aside from saying money. Though there may be a deeper connection as well (shareholders having hands in everything etc)

Dave the diver is backed by the multi billion company nexon iirc, it's not indie.

Those are fake indie games. They re-create the indie aesthethic to appeal to ethical consumers.

Dave the diver is not indie because it's published by Nexon.

Lies of P is made by a previously unsuccessful company, but it's also not indie. They made a lot of games in the past like Battlefield Online

Tangentially is 2023 chock full of great games because the pandemic held up the development of so many studios?

I know, they all announced that, but as a software dev, I really don't see why this should be the case. We largely just moved into home-office and continued working, often even at increased efficiency. I guess, building games might require somewhat more creative sessions, which are generally more productive in person, but I don't see that making a huge difference.
My impression was rather that they had the usual delays, with maybe a few hickups at the start of the pandemic, and then they just declared the pandemic the whole reason for the delays.

As for 2023 being so full, the pandemic meant lots of people were at home, consuming digital goods. It caused a massive boom in the gaming industry. I imagine, lots of studios were able to secure (bigger) budgets during that time, which are now coming to fruition.

There's no sudden new output.

Apples iOS privacy changes have killed a lot of the value in mobile markets, so many companies have been looking to diversify.