This is the 4453rd most frequent Japanese word.
大々的
Extensive; on a large scale.
In this sentence, "大々的に" describes the extensive and prominent manner in which the promotion was carried out.
その会社は新製品のプロモーションを大々的に行った。
The company conducted a grand-scale promotion for their new product.
Here, "大々的に" conveys that the reporting was widespread and prominent.
彼の功績は新聞で大々的に報道された。
His achievements were widely reported in the newspapers.
The use of "大々的に" in this sentence highlights the comprehensive and large-scale organization of the festival.