Fired from internship without cause

Started the 8th week of a 12-week remote winter/spring corporate finance internship at a global tech-enabled healthcare services firm. It was a neat internship, because I scheduled time around classes to work on reports, models, etc. It was decent experience, and I was paid hourly ($12). Work was somewhat boring and data-focused, but I was fortunate and worked hard. I got along very well with my team (seven other analysts), and I always asked for any work to help out. My manager, however, was very detail-oriented and criticized something of everything that I did. These were minor issues like coloration of excel tabs or parameters for reports that I wasn't aware of. Manager was not necessarily "mean" about the feedback, because it was mostly insignificant or something that I did not know, and I always thanked her for the feedback and made sure that the same mistake was not made again. She also called me out during meetings, which I was okay with, but the other analysts were very rarely criticized publicly even though mistakes were occasionally made throughout the team. Could definitely tell that something was going on, because my manager simply wasn't as nice to me as the other analysts. I just thought that it was because I was new and temporary, but everyone else on the team treated me very nicely and were helpful. I never said anything about this and was very professional and kind.

Logged onto work one day, as usual, and my manager messages me to meet. This is typical. Each morning, I typically meet with my manager and team entire team (we called it a huddle). Manager asked what I was doing, and I was completing a report that is done each Tuesday morning. She asks me to hold-off on that report while we chat, and I could notice a more serious tone in her voice. She said that someone else will be joining us, at this point I knew that something was up. Another person joined the call, and my manager said that my internship is "terminated" this morning. The additional person was an HR manager and said, again, that the internship is terminated and asked a few basic contact questions and if I had any questions. I paused for a few seconds and asked if there was a reason for this. The HR manager said that there were "attendance" issues and that employees are hired at-will. There were no attendance issues, except for class time that I had arranged with my manager and the team before the internship had begun.

Logged off the call and sent a kind and professional message to the HR manager and SVP of HR from my personal account with some basic contact information and asked for any rationale for the decision to terminate, since there were no clear attendance issues. I ended the email, asking if I could resign. Within an hour, the HR manager replied, accepting my resignation. Still confused on why I was terminated but am glad that I was not "officially" terminated.

The only other thing that I could think of was a mistake that was made the prior day. Manager asked me to put together a monthly report and gave specific instructions (via instant message) on what data to pull and gave an example report from the prior month. I followed the instruction carefully and replicated the file. Finished within 2 hours and sent the report to my manager to review. She said it looked fine and told me send it to the same people from last time. A few hours later, she calls me and says that there was a mistake with the report and to recall the message. It was a simple correction. Turns out, the report had been done incorrectly for the past few four months, so I based mine off of something that wasn't completely correct. I recalled and replaced the message (with a note that the previous message was sent in error). Did not seem like much a big deal besides having to recall the message, had never done this before.

Still confused but am not upset. I do not believe that I did anything wrong. Am aware that companies hire people "at-will" but justification is typically given (or assumed) for terminating employment. I also had never heard of a company firing an intern so close to the end date, unless there was a major issue.

Anyone had/heard of a similar experience?