Why questions are harder in JEE if board and JEE syllabuses are the same?

JEE Mains and JEE Advanced are two different engineering entrance exams. JEE Mains is conducted just after 12th Boards in the month of April. Clearing Mains, you can get a rank and admission into the NITs (National Institute of Technology), IIITs, and various other colleges like Amity. Many private

Because the board portions has been reduced. Earlier, it was huge syllabus but now it has been reduced in boards but the JEE portions hasn't been reduced that's why it seems to be difficult.