Amazon Software Developer Engineer II interview questions

I got a call from recruiter and she shared me an assessment link to complete the test on HackerRank. There were four questions. Two questions were based on Data Structure and Algorithm based and two were theoretical based where I have to tell the approach and time complexity about the given two problems respectively. After clearing my assessment with positive result, they rejected me in resume(just not finding out the keywords). Why did they send me assessment link though?