The USSR could theoretically have done so, if they stuck with their vanguard party idea and didn't pervert it by using the power obtained to oppress people and otherwise commit human rights violations.

What your describing is a benevolent dictatorship. Having a party that's not beholden to the workers isn't socialism, in my view. The workers need to have control over society.

They ousted the Tsars and Mensheviks without elections. That's not democracy.

Sure, but this isn't a system of government.

Or an even more pure example in theory would be a hypothetical nation of 10 people, 3 of which are oligarchs. 3 people imprison the oligarchs and redistribute their wealth to the other 4, whether they want that or not.

This also isn't socialism. Socialism isn't just reappropriation of accumulated wealth, it's the control of all parts of society by the workers, including the workplace. If you've got 3 people deciding everything for the other 7, that's not socialism, in my view.

You'll find a lot of MLs online (and one I met in person): oh but China listens to and considers what's best for the workers and implements that!

1. No they don't (in the case of China)
2. Being considered is not meaningful control and is revocable at any time by just not listening...

My conclusion, socialism without democracy doesn't make sense and isn't a thing.