This means the person has to move to a country with 0% income tax for this to make any economic sense, so that's either Monaco or the UAE then. Very difficult for me to understand why someone is supposed to pay this tax in the first place, the business paid a whole bunch of other taxes in its lifetime.

I would understand if they'd tax the sale of the business.

That is actually the intention: to tax as if you sold the business. But with a payment in 7 yearly rates. The tax intends to tax the value of the company that is not yet taxed (on a personal tax level). It does account for already paid businesses level taxes.

Its purpose is to avoid business owners to move to a low-tax place 12 months before selling their business and then move back to Germany another 12 months later, thus avoiding any tax on the increase in value of the business.