It is hard to overstate how strong the push for object-oriented programming was. It even bled out into other fields like education (look up "learning objects"). You had to organize your programming projects into hierarchical classes and you would be ridiculed if you did not. Java and C# are a reflection of this era. It took 25 years for the obsession to die down. Basically, the gurus had to be given time to retire.
Object-oriented programming can work… but there are serious pitfalls that will make your projects harder to maintain and optimize. Deep inheritance is almost always a disaster.
The lesson is: don’t blindly embrace the latest things even if everyone is. Masses will lead you astray. Be critical.
The older you get, the harder to resist saying "I told you so."
When OO programming came in, it made no sense to me, and I've never used it. Everyone said I was too old to understand.
Thirty years later, everyone's snapping out of it and wondering wtf they'd been thinking.