Germany supplants US as the country with the best global reputation
The survey is based on governance, exports, culture, people, tourism and immigration/investment.
What kind of these factors were affected by Trump's presidence?
Though I'm not sure how his policy affected governance, at least, he must have deteriorated tourism, and immigration.
Tourism: He is an advocator of travel ban on Muslims
Immigration: He wants to restrict the flux of immigrants.
On the other hand, he trys to raise the quantity of exports.
Totally, he might have contributed to the US's drop.