The rich get richer because they buy assets with money they earn. Real assets put money back in your pocket and this appreciation is reinvested. They invest in assets that incur less taxes than income.
The middle class stay constantly struggling because they use their wages to purchase liabilities, liabilities they believe are assets. Cars, boats, homes, electronics etc. all are liabilities. Also, the MC pay the highest taxes because wages are taxed more than any other income.
The poor stay poor because they buy things, and they spend all of their money on things. Not assets, mostly liabilities and just junk. Clothes, electronics, and all manner of useless junk from China.
It is an easy equation to gaining wealth, and the wealthy understand it.