Sara, I'm glad you posted this.

I've been using the WP-Optimize plugin daily in 3 different WordPress installations. What I never really understood was why the existence of database remnants of previously uninstalled plugins always seemed to be maintained. I posted this question on the plugin's support forums here over 4 months ago: https://wordpress.org/support/topic/deleted-plugins-remnants-recreation?replies=5 and even though the developer was both polite and helpful, I never got a good idea on HOW to get rid of previous plugins' leftovers.

Months ago, I temporarily installed BuddyPress on all 3 of those websites and bits-and-pieces of the software still remain. Because of your previous post back on February 20th here: https://wptavern.com/new-plugin-detects-shared-terms-in-wordpress-ahead-of-taxonomy-term-splitting-in-4-2 , I started re-evaluating my usage of older plugins. Approximately 1 hour ago I disabled and uninstalled the WP-Optimize plugin, deleted my cache, installed this WP-Sweep plugin, and then ran the sweep. So far...So good. I'll let you know how things progress (one thing I noticed is that all 3 installations updated much more quickly).

(For me, the correct selection and usage of plugins can be confusing, frustrating, and quite a learning curve over time.)