They advance the causes of their masters, who make fortunes by manipulating and administrating government policy.
They are the party of big government. The Republicans were the party of big government in 1860.
No, in 1860 it was Democrats who doubled the national debt in just four years through their profligate & sometimes corrupt over-spending, not Republicans.
It was Democrats who spent what today would be $65 billion on the Gadsden Purchase, so Jefferson Davis could have the new transcontinental railroad pass near his home.
As for alleged "big government" in 1860 the Federal government was about 10% of its current size.