Has buffett made two mistakes and not one?

Buffett admitted in his 2008 Berkshire Annual Letter to shareholders that he made a mistake buying Conoco Phillips shares at the peak oil price. Looking at Berkshire's complete portfolio it seems Buffett has made one more mistake, that of buying Kraft shares. (This is my own opinion so take it with a pinch of salt.) The reason is pretty clear. The company's last ten year history shows that the company's moat is becoming weaker and weaker year after year. The net profit margins have shrunk from double digits to less than 5%. ROE has declined from low teens to around 8.5% which is way lower than the average of its competitors. Kellogg's has ROE of 79%, with a net profit margin of 9%, General Mills has ROE of 25% with an NPM of 9% and H J HEINZ also has better ROE and profit margins than Kraft. If inflation is a big concern due to pumping of liquidity by federal reserve, than interest payment on 18B USD worth of debt that Kraft has accumulated for acquiring businesses is going to eat up a lot of profits in the near future. The competitors are smaller compared to Kraft in terms of size but that do not make them vulnerable. Let us see how this investment turns out for Berkshire.