Interns: an internship is not guarenteed employment when the internship ends.
Also your getting an offer for employment does not always reflect upon you or your performance. (It can, but not always)
At best it’s a long, paid, job interview.
At worst (ideally) it’s real world experience that school cannot teach you. Your entire experience - not just the project you work on - is the lesson.
It’s not a guarentee for employment or career. It never was and never will be.