This is the 2708th most frequent Japanese word.
盛り上げ
"盛り上げ" means "to liven up" or "to boost enthusiasm."
In this sentence, '盛り上げ' is used to describe how his speech enhanced or energized an atmosphere.
彼の演説は、会場の雰囲気を大いに盛り上げました。
His speech greatly enlivened the atmosphere of the venue.
Here, '盛り上げ' conveys the idea of engaging and exciting the participants to create a lively environment.
文化祭では、多くのアクティビティで参加者を盛り上げます。
At the cultural festival, participants are energized through many activities.
In this instance, '盛り上げ' means uplifting the mood or spirit, typically in a social setting.