Why are all files (except index.php) being redirected to 'index.html'?
There is a Rewrite Rule written in .htaccess as,

# Pass all requests not referring directly to files in the filesystem to
# index.php. Clean URLs are handled in drupal_environment_initialize().
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !=/favicon.ico
RewriteRule ^ index.php [L]


This may be your problem.

There are few assumptions that can be the reason why its happening :


Please check the method you the using to access files.
It might be your server issue which does not provide correct access rights for accessing the files
Your files are not properly placed in correct locations.