I just spent the last three hours recovering from the 5.0 upgrade, I saw the same Kingcomposer disappearing like in your screenshot. I had to completely remove database and filesystem, install wordpress 4.9.8 from scratch, then reload from this morning’s backup. (Backup every day!)
Now, I cannot upgrade to WordPress 5.0 until Kingcomposer has a migration solution to WordPress page builder blocks. This will put Kingcomposer out of business I guess. Anyway, good luck..
