OOP is not important because of itself, but because of what it
takes with it. Something that deals with the capability to
abstract and isolate, group things together end expose only the
parts that are required to interact together. This is a common
engineering technique called "modularization", that allows to
create complex systems as aggregation of simpler ones, without
to take care of every single details at high level, and that
require components to be replaceable, even without them to be
exactly the same. Those "engineering concepts" have been tried
to be kept into the software development from the time software
product themselves had become larger than the "single developer
capability", thus requiring a way to make developers to work on
independent pieces, and let those pieces to interact together.
That said, those principles are not necessarily found only in
OOP (it the computation theory is valid, there are infinite
possible methods to come to those results). OOP is simply a
successful attempt to put t