Top of the flops: just what does the games industry deem 'success' any more?

Back in 2013, having bought the series from Eidos, Square Enix released a reboot of the hit 1990s action game Tomb Raider starring a significantly less objectified Lara Croft. I loved that game, despite a quasi-assault scene near the beginning that I would later come to view as a bit icky, and I wasn't the only one – it was extremely well received, selling 3.4m copies in its first month alone. Then Square Enix came out and called it a disappointment. Sales did not meet the publisher's expectations, apparently, which raises the question: what were the expectations? Was it supposed to sell 5m in one month?