documentclass{beamer}
usepackage{multicol}

begin{document}
begin{frame}{Why does this happen?}

begin{multicols}{2}
begin{center}
  begin{enumerate}
  item Text
  item More text
  end{enumerate}
end{center}
columnbreak

begin{center}
  begin{enumerate}
  item Text
  item More text
  end{enumerate}
end{center}
end{multicols}
end{frame}
end{document}