Clone games make a profit?

Four and a half years ago, Fight Club appeared in runet, an online game that won incredible popularity and brought huge profits to its developers.

Since then, clones of BK began to multiply in large quantities:
Arena
Territory ,
Carnage
Free land , etc.

All these games are from the “We also made BC” series. The principal differences are zero, unprincipled ones are not worth talking about.
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From all of this afterBK-shnoy series, it is possible to distinguish, perhaps, only TimeZiro .

I do not understand. Why reinvent the wheel and hope to make money on it?
Quake differs from the Halflife, and the Halflife differs from the Counter Strike ...

Why are Russian developers of on-line games so much hooked on cloning a BC?
A fresh idea and a bit of fantasy don't pay off much faster than the old and boring CD with new and not always the best pictures?