Indian Performing Rights Society Ltd vs Sanjay Dalia

So, you know how we have this whole ' assignment of contract' thing, right? Well, in this case, IPRS (a music rights society) assigned a contract to this guy, Sanjay Dalia, to run their operations in Mumbai. The assignment was in writing, and Dalia even got a commission out of it. But, when he messed up big time, IPRS said, "You know what, assignment is revocable." But Dalia's all, "No way, assignment is an onerous contract, and we can't just terminate it willy-nilly." The Bombay High Court agreed with Dalia, and IPRS had to pay him some damages. My take? The court's decision was a bit odd. I mean, if assignment is onerous, why did IPRS even assign it?