I don't know what to think about these conspiracy theories.
If world centralization was the goal of central bankers, I think they had to achieve some form of unification. They needed to end brexit, the catalan independence movement & similar actions which are occurring around the world as people lose faith in governments and authority figures. They needed to quell opposition to central banks which pervades nations like iceland, russia, ireland and hungary.
There were many steps which needed to be taken to guarantee centralized unification before a crash happened. That would make it easy to consolidate in a post crash era. They also needed to synchronize events so that europe and the united states both crashed at relatively the same time. If their goal was centralization, they couldn't have europe crash only for martial law or a similar equvalent to be established. That would offset efforts to influence similar events in other countries which could set back their timetable by decades.
Anyways, long story short. Whatever the goals or plans or central bankers are: only they know. Everything else is purely vaporware speculation.
Still it can be interesting to talk about and discuss, if you can find anyone who is willing to risk being branded a "conspiracy theorist" who believes astronauts never landed on the moon.