This isn't Tom the small business accountant from rural Ohio commenting on Germany's immigration policy on a facebook post. It's someone who controls more money than the GDP of multiple entire countries, and who has already shown an interest in using his companies to influence geo-politics based on his opinions in the moment.
If anything, you should be concerned that a single individual can make choices about global politics without discussion or legal safety guards - which has historically caused some issues in the place that the AfD comes from.