Lloyd George had a serious axe to grind.
He had his own failures to hide, and Kitchener made a good scapegoat.
Slandering the dead.

"However, since 1970, new records have opened and historians have to some extent rehabilitated Kitchener's reputation. His strategic vision in the World War is now praised, especially his laying the groundwork for the expansion of munitions production and his central role in the raising of the British army in 1914 and 1915, which provided an army capable of meeting Britain's continental commitment."

https://www.princeton.edu/~achaney/tmve/wiki100k/docs/Herbert_Kitchener,_1st_Earl_Kitchener.html