It is very long run. Industrial revolution was disaster for average worker for example. For that matter, all the tech that allowed chattel slavery made whole class of people poorer and significantly worst off.
The accumulation of power and money by smaller group of people means loss of power by poorer people. Those with power then use the power to their own benefit while poorer people dont have that option and become even more poor or worst off.
Just as an example (ironically from google!): "Google co-founder Sergey Brin has spent $82 million to oppose California's proposed wealth tax."
This is a man that has more money that he could ever hope to possibly spend, and he's spending an absurd amount just because the mere thought that he might benefit from the society he lives in and should contribute back to it apparently infuriates him.
Sergei's wealth is mostly tied up in Google stock that has appreciated a lot. A higher capital gains tax would soak him without unduly distorting the economy and incentivizing capital flight out of CA.