IMO Marxism was doomed to failure from its inception. Although there were elements of an attempt to understand the human character, it became a futile idealistic exercise and the fall of the USSR proved this point. In other words, the philosophy of Marxism was reasonably complete - man would come through the 'fire' of Socialism and be reborn as a person who does not care for himself but who has a collective responsibility. The collective idealist man cares for others more than he cares for himself.

Additionally, the means of production (industries and factories) will be the best after the rise and fall of the wealthy industrialist after the worker realises that he alone owns the reins to power.

Everyone is then equal, there is no private property, you work with a smile on your face for your neighbour and your 'collective'. Everyone has a Paradise on Earth.....yada, yada, yada...

Where did it go wrong? Where will it go wrong in the future?

In a phrase - you don't understand human beings. Human beings are selfish. They don't care beyond their front doors. They want cheap entertainment instead of information. They want to work as little as possible for the greatest payoff. Will it ever change - of course not! That is why the USSR economy went into bankruptcy - some workers were off to their dachas whilst others in the same factory had to work extra hard to cover their lazy asses.

IMO if you want change to Socialism, you need to build a new philosophical base which gives a full description to man's motivations and needs, the old is dead. You need to forget Hegel and Marx and look to a fusion of Capitalism and Socialism. If you don't you will always fail...