So, when you create content/contributors/index.md, you are actually creating a leaf bundle, but it isn’t in a contributors section, it’s in the root section, thereby using the layouts/_default/single.html template.
There are different approaches to get that content into place, but if you just want that single page you can do the following:
Add layout: contributors to your front matter, and
Move layouts/contributors/index.html to layouts/_default/contributors.html
---
title: Community Contributors
date: 2022-04-03T11:00:02-04:00
draft: false
contributors:
joe: ...
jane: ...
layout: contributors
---
some content