upstart

One who has suddenly gained wealth, power, or other prominence, but either has not received social acceptance or has become arrogant or presumptuous.

• upstarts […]they call in reproach mushrooms
• But electric vehicles and the batteries that made them run became ensnared in corporate scandals, fraud, and monopolistic corruption that shook the confidence of the nation and inspired automotive upstarts.

The meadow saffron.

Acting like a parvenu.

Self-important and presumptuous.

To rise suddenly, to spring

• Th' Elfe therewith astownd, Upstarted lightly from his looser make, And his unready weapons gan in hand to take.
• the beauteous beast Scared by the noise upstarted at our feet