Mail armor is known to have a disadvantage from stabs due to the point going through the rings of the mail, but laminar only seems to have a disadvantage when stabbed under the gaps of the segments, like scale, so how come there was a transition from laminar to mail?
Mail was used by the Romans as early as the Punic Wars against Carthage, 200 years before Segmentata appeared. It never fell out of use. Segmentata (what you mean with laminar) was expensive to mass produce and was not as great in defending a soldier as you think it was.
Mail was easy to produce, was lighter, protected very well against slashes and relatively inexpensive too.