Complex sentence: Hamann asserts personal motives for Jetzinger's tendency to illustrate nearly every statement in Kubizek's book as an ex post modification of facts, claiming Jetzinger was economically motivated, because the previous release of Kubizek's book supposedly undermined the sale of his own work.
Split into simpler sentences: Hamann asserts personal motives to Jetzinger's tendency to illustrate nearly every statement in Kubizek's book as an ex post modification of facts. She claims Jetzinger was economically motivated, because the previous release of Kubizek's book supposedly undermined the sale of his own work.