why does RewriteCond %{SCRIPT_FILENAME} !-d break my RewriteRule
snippet in htaccess

why does RewriteCond %{SCRIPT_FILENAME} !-d break my RewriteRule

user9398

Options -Indexes

RewriteEngine On

RewriteRule ^$ index.html [L]

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/index.html$
RewriteCond %{REQUEST_URI} ^/.+$
RewriteRule ^.+$ index.html [L]