If the wealthy actually wiped out the working poor, the wealthy could not survive, QED.
If you seek a biological analogy, the social fabric you refer to is much more akin to parasitism than Darwinism. The wealthy don’t seek to wipe out the poor or for the poor to even be a minority! God forbid.
On a broader level ..
Mutations are more-or-less random. They can lead to either greater/lesser fitness or greater/lesser competitiveness. Differences are typically fairly marginal, and absent a catastrophic event (like dropping antibiotic on a dish, above, or maybe a human plague or an asteroid impact), the timespans involved are long.
There is a lot of attention paid to the word “selection”. The point (above) about mutating-to-greater-fitness vs. mutating-to-greater-competitiveness is probably relevant here: If populations are competing for limiting resources, then yes, there is competition and there is selection through competition. Maybe this has analogies in European social history.
But, if resources are not limiting, selection may not be attributable to mutual competition. This may fit the Russian scenario, historically: Unlimited resources, small population. This may be what Kropotkin tries to describe: Social cooperation is feasible.
BUT this does not mean that mutation to greater fitness is not occurring regardless, because of the selective effect of the environment: Even if populations are not mutually competing, biology is still adapting to environmental changes over geological time: Ice ages come and go, people wander into new ecological niches and are fit or not fit in the new niche. The planet is a dynamic entity - it never stops changing. It is still cooling, plates are moving, it is moving through space and getting sporadically and suddenly irradiated or bombarded. Mutations don’t stop occurring, either, over generations. So changing people find themselves accidentally adapted or not adapted to changing environments, and thriving or dying out by inference. This is essentially a Darwinian process too.
Individuals that mutate too fast or too slow for their environment die out. Two dynamic processes are matched: Biological change, and geological change. The former is a product of the latter, we are perfect in our imperfection.
Nobody escapes Darwin.