The phrase "gained ascendancy" is grammatically correct and can be used in written English.
It means to gain power or authority over something or someone. Example: After years of hard work and dedication, she finally gained ascendancy in the company and became the CEO.
With the advent of national nautical almanacs, the equatorial system, which is better suited to observation and navigation, gained ascendancy.
As the English East India Company gained ascendancy in the 18th century, Thomas Christians faced new challenges.
Although Juan Pacheco, marqués de Villena, initially gained ascendancy over the king, others vied for royal favour.
With the administrative reorganization that started in the late 1970s, Catalonia became a comunidad autónoma ("autonomous community"), and Catalan once again gained ascendancy in eastern Spain.
Neither the Ricardian classical economists who preceded Keynes nor the Friedmanite neo-classical economists who gained ascendancy from the 1970s assign much of a role to uncertainty.
Among the various systems of vocalization that were invented, the one fashioned in the city of Tiberias, Galilee, eventually gained ascendancy.
With time Rome may gain ascendancy over the north.
It's as if Manhattan has to be disgraced and humiliated for any other borough to gain ascendancy.
Instead for all their lack of air power, drones and high-tech equipment, the Taliban are gaining ascendancy.
Photography is in the service of the post judgmental ethos gaining ascendancy in societies whose norms are drawn from the practices of consumerism.
The latest GDP update shows that froth still dominates (the flat white reference being a nod to a tech/digital economy that has yet to gain ascendancy).
