Hell redirect, what to do?

Question

htaccess

Help plz!
There was a site with links in the index with the extension .html
Site on WordPress, registered the following in htaccess
RedirectMatch /(.*)\.html$ /$1\ - now it redirects to normal links
BUT!
Now, instead of the main page, I have site.ru/index
index without an extension, nothing helps, I googled, but apparently it’s bad, I don’t rummage in redirects at all. Please help!
Here are all the entries from the file
# BEGIN WordPress
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
# END WordPress
RedirectMatch /(.*)\.html$ /$1\