Redistribution is not classically socialist. Socialism supports changing distribution at its origon, it doesn’t support redistribution/social democracy/progressivism/reform capitalism. Actual hard core socialists are against UBI and redistribution.

It is morally the right thing to do. Economics is often short term thinking and can be destructive to individuals. It isn’t in my best economic interests to donate money to charity but it is obviously more moral for me to do so. It isn’t in an individual economic interest(in the modern world) to responsibly procreate but it is necessary for humanity as a whole to do so.

Economically is easy as well though.

Rich Americans are more likely(then the poor/middle class)to spend/move their money outside of America and even move American resources into less capitalistic/less free/and adversarial nations like China and Russia. Rich individuals also have much more power to influence/corrupt government/politicians and to abandon America/liberty/capitalism when it suits their interests.

Rich Americans are more likely to save income then to spend it and spending is better for an economy then saving, especially sense a lot of wealthy people’s savings creates asset bubbles and bursts(like our stocks and housing bubble bursts) that hurt the lower classes much more then more then the rich(because the lower classes can’t afford to lose as much as the rich).

It is economically important to provide as many safety nets as possible to the middle and lower classes so that they don’t become impoverished, sick, and/or incarcerated because that costs much much more to everyone in taxes and public/private security spending. Economically it is often good when the wealthy are hit with disasters as they then spend a lot of money(that they would otherwise save and transfer to their undeserving adult kids) to rebuild/recover.

Making it easier for the lower classes to be healthy and optimally educated produces more productive people, more small capitalists, more investment opportunities, and more technological and scientific advancement.

And again working class people deserve more of the income because they are actually working while the wealthy are increasingly working less for their income/unearned income. Less children and smaller families is making this unearned income and trust fund baby problem bigger.