SendGrid Software Engineer Intern interview questions

I was contacted by the HR of company. The process is straightforward, which is a Phone interview and followed by an on site interview. Phone interview is just a process of knowing each other. Two engineer interviewed me during the on site interview. First one asked some general questions. For example, how to shuffle an array (programming) and some other OOP concepts such as difference between instance and class, what is constructor, inheritance, abstract class, pure virtual function. The second engineer asked retrieve several email lists from different url and return what email address occurs multiple time in these url. The email address are stored in the JASON format in the urls. I used a python package to retrieve the information. Everything goes very well during the interview. I solved the problem very quickly and was told by the HR that the decision will be made in a week. However, I was declined a month later after sending couple emails to the HR.