This comes from the Preface to David Gilmour's excellent biography of Curzon:
Curzon's reputation thus survived the first two verdicts of history. In the early 1930s, however, Lord Beaverbrook launched an assault on it that lasted for nearly 30 years and ensured its virtual destruction. In a series of racy and tendentious books the newspaper tycoon directed a crescendo of abuse culminating in the allegation that his victim had been 'inconsistent, unreliable, untruthful and treacherous'. His principal charges were that Curzon had 'changed sides on almost every issue during his long career' and that he had given Asquith 'an absolute pledge' that he would not serve under Lloyd George in 1916.These are particularly odd charges as in his own lifetime Curzon was often attacked for being too inflexible.
Beaverbrook's judgements were accepted with a strange lack of inquiry by some distinguished historians, who repeated his statements and in some cases developed them so that it soon became almost obligatory to describe Curzon as a 'turncoat' or 'deserter' always joining the winning side. Pre-eminent among them was A.J.P.Taylor, who portrayed him as 'one of naure's rats', a weak and irresolute figure who in 1922 'deserted Lloyd George as successfully as he had deserted Asquith'. Another highly respected scholar, A.M.Gollin, took up the theme of Curzon's 'political somersaults', claiming that before the First World War 'he often advocated certain definite policies, only to change his mind at the last moment and reverse his course'.
It was not till the late 1960s when Kenneth Rose published his biography of the late Viceroy and Foreign Secretary and David Dilks his two volumes on Curzon in India that there was even a partial rehabilitation. We then went through a period of too many historians refusing to see anything good in an unashamed imperialist, despite his interesting and sensitive descriptions of Persia and Central Asia and his well known determination to preserve Indian culture.
Why exactly would any reputable historian follow the lead of a somewhat disreputable newspaper magnate in historical matters?
He was the embodiment of a cause no one believed in anymore. So he had no champions. And he was dead and hence in no position to defend himself.