OK well there's not a completely clear 'answer' to Taylor's change of sentiment.
Note that he was educated at a Quaker school and came from a pacifist background, so would have been more inclined to condemn any policy that (intentionally or unintentionally) resulted in war.
The best answer however is that he changed his view due to what Churchill (in The Gathering Storm) called "the afterlight [which] softens many of the severities of contemporary controversy". i.e., the passing of time between the 1930s and 1961 allowed Taylor to distance himself from the emotions of the time, which thus enabled him to make a more balanced and reasonable assessment of the events, the policy and the
policymakers.
Remember that A.J.P isn't a true revisionist though; e.g.his condemnation of Chamberlain and the appeasers as being characterised by "timidity; blindness; and moral doubts"
However in the exam it's really not that relevant to mention his former anti-appeasement background - just focus on the more moderate view he puts forward in 'Origins'.
I definitely wouldn't say anything about him 'wanting to be controversial' - that's quite a large premature assumption.
His opposition to the orthodox view may also have come through his methodology: he relied heavily on diplomatic documents as his sources, while Cato, Churchill etc (who confirmed the orthodox view) did not examine these as heavily, instead using other sources. (e.g. Churchill used his political experience to justify his authority)
Hope this makes sense and helps!
