I can tell you it's because he's actually a very skilled engineer. He will blow the interviews completely out of the water. Easily top 1% or top 0.1% of candidates -- other startups will tell you this as well.
The problem is when the job (or work-trial in our case) actually starts, it's just excuses upon excuses as to why he's missing a meeting, or why the PR was pushed late. The excuses become more ridiculous and unbelievable, up until it's obvious he's just lying.
Other people in this thread are incorrect, it's not a dev. shop. I worked with Soham in-person for 2 days during the work-trial process, he's good. He left half of each day with some excuse about meeting a lawyer.