Magic the Gathering players are intimately familiar with the term :)

I think it’s from YouTube. “With that, we can delve into [topic]” was part of the vocabulary for video essays for years. It always joined an introduction’s closing thesis statement with the rest of the video content.

The dwarves of Moria are notable for having delved to excess.

It seems it is common in Nigerian English, from where in ended up in AI datasets.

I’ve only ever seen it used in magic the gathering

I'd see it occasionally, usually in bullshit corporate writing replete with other buzzwords, which is probably where the LLMs picked up on it.