Do you think it is possible that what Crocodile tried to do in Alabasta, frame the king, make him look like a bad ruler, cause a rebellion and take over as king; is exactly what Doflamingo did in Dressrosa?
We saw on Marineford that the two did not exactly get along but had something of a history with one another. Could it be possible that they are from the same generation or one came soon after the other and Crocodile did not like that Doflamingo was getting further in standing than him so he tried to catch up by also becoming a king adn getting an ancient weapon at the same time. Dressrosa is an island with a lot of history maybe Donflomingo also has some ancient power under his sleeve.
Sorry if someone already said this and I'm being repetitive.