Hi Sudar,
• I believe these were sploggers, so I don’t know how they were created or if they were directly inserted into the DB. They just kept appearing until there were close to 145,000.
• No, it is not a multisite.
• As you requested, a screen shot of the first page of users with “None” roles is attached.
• I also attached a screenshot of the bulk delete users admin page. Note that the select list to delete users (at the top) includes: “none (0 users)”, while the user list shows 140,103 users with “none”.
• I attached a screenshot of the plugins list as well, for you to review for potential conflicts.