How do I redirect command output to vim in bash?

You can use process substitution (this also works with applications that can't read from STDIN):

vim <(ls -la)

Or use vim's function to read from STDIN:

ls -la | vim -

You're really close on your own. You were just missing one character.

ls -la | vim -

Here's another approach, hopefully to teach someone something new.

If you know that the command :r !ls -la works inside vim, you can do the following to open vim and make it run the command as soon as it opens, straight from bash:

vim -c ':r! ls -la'

This is the equivalent of opening vim then executing the command :r! ls -la. This should work with any vim command, where the command comes after the -c option.