Complex sentence: Post 1945, the FC engaged with the wider evangelical cause, but after its growth in the early decades, it began a statistical decline that, except for a short period in the 1980s, has continued to this day.
Split into simpler sentences: Post 1945, the FC engaged with the wider evangelical cause. But after its growth in the early decades, it began a statistical decline that, except for a short period in the 1980s, has continued to this day.