Assuming a well regulated market with the rule of law and minimal barriers to entry and plenty of innovation happening, sure.
Take those things away through bad/ineffective government and you could very easily end up in a society where those in power use their power to stop others from innovating or accumulating any wealth.
Long lived institutions focused on consolidating and preserving their power can have a similar effect to long-lived people. The Catholic church's role in the Middle Ages, for example.
Or just mildly competent investors. If the economy is growing their wealth will compound. If the economy is shrinking they’ll still be rich and everyone will suffer.
Some new competitor will eventually crush MS and Amazon. To stay extremely rich forever, Bezos and Gates will have to also be great investors.
Then some other person like Musk comes with new ideas that blow even their massive fortunes out of the water.
Long term dominance in an eternal-life society is certainly not possible.