According to Royalblog:
The reason for the tribute is the 70th anniversary of the “coup” that King Mihai committed…
The coup was daring because Romania could not expect the allies to come to its aid; and the USSR especially was not happy with the turnaround. Stalin wanted to control Romania and didn’t want it as an ally. They invaded, installed a communist regime and in 1947 expelled the King from the country.
…presidential candidate…sees the action of the king “as a milestone in our history. Mihai…opposed communism and is also today a moral compass and a unifying personality….”