Good going for US corporate bonds

Today's Wall Street Journal has this interesting news item. As Federal Reserve is tightening the monetary policy ,thus increasing the interest rates on treasury securities, the foreign investors are shunning US treasuries and embracing US corporate bonds. The buying of US corporate bonds by foreign investors is at record level this year. US corporations are enjoying the benefits as such enthusiasm of foreigners is keeping their borrowing costs low , increasing their profitability. It is particularly surprising that Japan has purchased a lot of those corporate bonds when there is no dearth of opportunities in Japan's booming market. Is this another evidence of the theory that it is a global savings glut which has created huge US current account deficit not the profligacy of US government?