Turkey and Saudi Arabia are the two biggest Sunni economies in the world, and until 2011, were aligned economically and militarily. However, they had a major difference of opinion on the subject of the Arab Spring.
Turkey is a much more politically moderate and democratic than Saudi Arabia, so it supported the toppling of dictatorships and authoritarian regimes so that it might have a better relationship with the new rulers. In addition, they had no outside interest in the stability of those countries, as their relationships were pretty rudimentary.
Saudi Arabia is extremely conservative and authoritarian, so the toppling of authoritarian regimes in the area is something they most certainly do not want to encourage. But they have a secondary interest: Saudi Arabia is wealthy, but even the wealthy require servants to do menial work. This workforce was previously supplied by many of the authoritarian regimes that were upended, so to disrupt the stability of those countries is to directly disrupt the stability of Saudi Arabia.
The former friends have suddenly become enemies, but Saudi Arabia has the upper hand. It's much wealthier, and has much stronger ties with major powers like the US. So Turkey has a vested interest in displaying the skullduggery that has always gone on behind the scenes in Saudi Arabia in hopes of disgusting Westerners, who will boycott Saudi Arabia and perhaps switch their allegiance to Turkey.
