I've always wondered if there's a story behind modern.ie using chunked .rars over e.g. non-chunked .zip. What were the technical/human constraints that lead to

I've always wondered if there's a story behind modern.ie using chunked .rars over e.g. non-chunked .zip. What were the technical/human constraints that lead to that solution? Was the team agonising over conflicting goals? Or was it as simple as "Alice already knew it"/"Our tool chain already supported it"?