In the currect case, it's island
naivity; these birds simply know no terrestrial
predators, and haven't for a long time.
With respect...the critical point the video makes (as it relates to a
general dinosaur susceptibility to predation) is that an incubating parent
is likely to suffer distasterous predation because of a couple of nesting
imperatives: if you leave the nest you lose your eggs/hatchlings--i.e., you
lose either way; and it is almost impossible to defend a nest at night.
Neither of these points relates to naivety--rather, they relate to the eye
physiology of (in this case) mammals vs. birds; and (in the case of large
non-avian dinosaurs) an inability to nest in remote or hidden locations (a
strategy the albatross had successfully employed until the dreaded mouse
colonization).
For me, the now-known diversity of Late K mammals ranging into racoon-size,
and the general tendency/rule of organismal exploitation of available
resources, leaves the hypothesis of large scale nest predation (as seen by
almost all extant large egg layers) with two questions: could non-avian
dinosaurs see at night?; and could non-avian dinosaurs escape predation by
nesting in locations remote or hidden from small nocturnal predators.