Why is it difficult? Bcos Buddha preached this sutra according to his own understanding (highest wisdom) & not according to our unenlighened beings understanding.
There is only ONE single sutra which Buddha declared as his highest teaching - Lotus Sutra which was the true purpose of his advent in this saha World. He declared All buddhas including himself fr past, present & future attained true Enlightenment thru this Sutra.
None of the provisional Sutras that was preached for past 40yrs will enable ppl to Enlightenment. Buddha declared in the Lotus Sutra ( 妙法连崋经) " honestly discard the provisional teachings, i shall reveal the truth".