Peter Ward (and others) believes that ammonites went extinct because they bred/fed at shallow depths. In contrast, he claims that nautaloids survived because they bred/fed in deeper water. I'm don't know what his take is on squids and octopus.
The hypothesis is that the deeper depths were "buffered" from the carnage that was occurring in the near-surface marine waters. This idea is supported by the observation that Maastrichtian benthic biota tended to fare a little better than did their pelagic counterparts.