I'm not sure this is correct; do you have a citation? Owls, granted, have
huge eyes and the overall shape maximizes sensitivity. However, owls have
1) much greater sensitivity than many other nocturnal animals (so the fact
that they have larger eyes than crocs, proportionately, does not mean that
crocs have an advantage) and 2) owls also cannot sacrifice too much acuity
(they do still sacrifice acuity to a substantial degree, but have limits).
Because acuity and sensitivity have conflicting shape requirements, the
eyes of animals that maximize one parameter must generally have huge eyes
if they do not minimize the other.
I hate to use such fait accomli arguments such as: placentals are the
dominant form of mammal; their characteristics may have had something to
do with this.
Indeed; and so one might suspect that reproductive mode has made a major
difference >within< mammals. Arguing across major clades with other
differences, however, is more difficult. In fact, what is really striking
about modern placentals (comparing them to their Mesozoic ancestors, as
well as other living clades) is their major presence as medium to
large-bodied, terrestrial forms. Given that dinosaurs fell into the same
category in the Mesozoic, we might expect that key to being viable in that
morphotype lies in the similarities between placentals and dinosaurs,
rather than the differences.