Complex sentence: From early periods solar gods such as Re had played an important role in Egyptian state religion because the distant but universal power of the sun fitted well with prevailing ideas of the supreme power of the king both within Egypt and beyond its borders.
Split into simpler sentences: From early periods of the Egyptian kingdom solar gods such as Re had played a very important role in Egyptian state religion. This is mainly because the idea of the sun as a distant yet universal power was close enough to the prevailing ideas of the supreme power of the king both inside Egypt and beyond its borders.