The company quickly took action and reasserted its dominance in the market against competitors' challenges.

reasserted 是动词 reassert 的过去式，由前缀 re-（表示"再次"）和动词 assert（主张、断言）组成。reassert 意思是"再次声明、重申"，在商业语境中常表示"重新确立（地位或优势）"。