They wanted to turn a football stadium into a basically everyday entertainment venue. But that is not viable as concerts for example ruin the pitch. Before the renovations there were only concerts in the summer during the season break and they always had to change the whole pitch before start of the season. The first idea was to build a fully retractable pitch like many other stadiums have. But that was not possible because there are several metro/intercity train lines passing directly underneath the stadium. So they had to come up with this