You can hardly blame them for allowing themselves to be outdone by GILD’s $11B offer.
$11B seemed like a lot of money at the time. It's not a lot of money when you can potentially hold a monopoly on a treatment that works for all HCV patients. Within a non-durable treatment group (unlike HIV) of 170m patients worldwide. GILD knew this and BMY didn't. GILD wasn't going to get outbid and BMY lacked the insight and didn't do the math.