See your comment as an example. Why list all links at the bottom rather than in-place?
Hiding in the URL is a favorite feature for scams and pranks
As for <details>, you run into the problem that it’s a block-level element; it’s dubious using it as an inline-level element, though it’ll probably work well enough (I say probably due to uncertainty about screen readers) despite being nominally invalid, given that it’s not an element that will automatically close a paragraph tag like <div> does.
I think links at the bottom is generally foolish, taking more effort for both reader and writer, and never do it that way, interspersing them in the text, usually surrounded by angle brackets as has historically been the way of delimiting URLs in plain text.
This avoids requiring both long scrolling and interactivity.
For my site, there are other options that I'd like to explore. Tooltips for smaller things (like definitions) maybe sidebar notes for large screen sizes, and inline notes (like show/hide inserting it between that line and the next) for mobile.
I'll look into those.
Searchability. You want footnote content to be Ctrl+F-able.