Complex sentence: The motors for the Ae 4/8 were heavier than those of the Be 4/6, therefore the Ae 4/8 was planned with two more idle axles from the beginning.
Split into simpler sentences: The motors for the Ae 4/8 were heavier than those of the Be 4/6. Therefore the Ae 4/8 was planned with two more idle axles from the beginning.