The verb 'help' takes to-infinitives and bare infinitives but bare infinitives are said to be the most common in casual text; as also used in this example sentence.
今度は彼はくだけた服装をした。美々しいスーツは場違いである事に気がついたからだ。
This time he dressed down, having realized that the smart suit would be out of place.
花瓶はテーブルから落ちて粉々にくだけた。
The vase fell from the table and crashed to pieces.