I think it simply died in the nets before it was pulled onto the boat.As these creatures live in the deep sea, I'm sure the change in pressure killed it. One reason why it would be very difficult to capture one alive.
If you'd like to know more about these creatures, check out The Search for the Giant Squid: The Biology and Mythology of the World's Most Elusive Sea Creature by Richard Ellis. A very interesting read.
The body of the colossal squid is much bigger than the giant squid, which can weigh up to 900 kg, 2,000 pounds when fully grown. A giant squid's tentacles can be up to 13 meters long, compared with five meters on the recovered creature.No word on the tentacle length, besides the one they recovered had 5 meter tenticles..