It is known as a retro trend and has happened throughout the
history of high-fashion. The why is difficult to determine and is
rarely agreed on by experts in the field.
Fashion trends go through a cycle. The trend starts as something
new that trend setters wear then eventually becomes over worn and
the population becomes tired of it. Years later that trend will be
tweaked a little to fit in with the fashion standards of the time.
This is retro fashion. The new retro fashion will then go through
the cycle again. Another fashion trend is vintage. This is when the
piece of clothing is the exact same as it was when it was first
created, so no new tweaks were added. There is no definite answer
to why different styles come back, but designers know the fashion
cycle very well and can predict what era of fashion they should
bring into their collections.