The US political parties are not as different as you think.
Those pro-corporate uber-rich Democrats? They have what are called “class interests.”
Those rightwing rich Republicans? They also have what we call class interests.
And the class interests of those groups happen to be exactly the same. So you would expect wealthy “Democrats” to be allying with wealthy “Republicans” more often than you might think. Why? They both have exactly the same class interests. In fact with increasing inequality, we will even see “the end of ideology.” There won’t even be any ideology anymore. Instead there will simply be groups acting politically in precisely their class interests.