Do we even know yet what the motivations of this coup are?
Yes. They listed them at the start. They want to basically 'restore' (in quotes because its debatable whether it really existed ever) liberal, secular, democracy.
They feel that the current administration is too authoritarian and too islamic and they need to be removed by the...traditional Turkish method.
Well, that what they say their motivation is…doesn't necessarily mean it's their real motivation.
Yeah, literally every movement in the world says they support democracy, from Nelson Mandela on one side to the Democratic People's Republic of Korea on the other.