Ye Jianming was the sole businessman among the group of Chinese and Czech government officials who gathered two years ago outside the presidential summer residence. In just two years Mr. Ye’s company, CEFC China Energy, had spent more than $1 billion on deals in the Czech Republic. He hired former Czech officials, including a onetime defense minister. Mr. Ye was even named a special economic adviser to Mr. Zeman. Mr. Zeman, in turn, became a big backer of Beijing.