are they a super admin or PU? If SA, they can do anything and enrol anyone...If PU, you might want to check their Resources to see if they have access to something they shouldn't 

They are a SA but are new to working in an LMS and though I am also a SA, for the purposes of this post, pretend we work in two totally different companies but share the same platform (using different categories/branches etc.) and this SA is unaware of what they’re doing and doesn’t mean to be doing it. 

I am trying to find out what settings/rules they might have set up in order to connect with them to correct it. What settings would one be using that would automatically enroll new user profiles into every single course in the LMS? They wouldn’t necessarily even know this answer themselves which is why I was trying to see if anyone here could have insight so then I can set up a meeting to guide them through this.
 

hmm...you will need to soak with your SA to set some limits I guess…

If you want to automatically enroll all new users in your platform to a set of courses/LPs, you will need to create a Group. We usually add a custom field to the user profile to identify them as “new” you can add a hire date, a code, or other piece of data...Once you have the group in place, you can use the Enrolment Rules app to associate the group and courses. Turn ON the rule and anyone in Groups will be assigned those courses.

https://help.docebo.com/hc/en-us/articles/360020128579-Activating-and-Managing-the-Enrollment-Rules-App

I appreciate you assistance but see I am not doing a great job of explaining/may have left out some details regarding this situation. 

Our platform is already set up with different groups, etc., etc. etc. on both sides. This other SA must have “flipped some sort of switch” because this was not an issue up until the last week or so. Previous to the last week when they entered new users, those users were being enrolled properly but now suddenly something has changed and everyone is being enrolled into our courses and something they're doing is superseding our own enrollment rules, groups, etc. that we’ve set up on our side. 

What settings would someone use/create to enroll all users into all of the courses? I want to know the answer to that question and from there I should be good to figure tout the rest on my own.

please remember that a super admin can perform any function in the LMS so to track down what has occurred, you’re probably best off using the Audit Trail app to find out what happened...We had something similar happen on one of our sites where an admin enrolled over 100,000 users into courses...it cause all kinds of issues and slowed the system down. The audit app helped us too find the admin and see what occurred.

https://help.docebo.com/hc/en-us/articles/360020124059-Managing-the-New-Audit-Trail