This came after an impasse between moderates and progressives. According to the New York Times:
Approval of the budget was a milestone in Democrats’ drive to enact their top priorities — including huge investments in education, child care, health care and paid leave, and tax increases on wealthy people and corporations — over Republican opposition.
IT'S OFFICIAL: U.S. House passes $3.5 trillion budget reconciliation resolution.
Big win for @USProgressive.
Historic loss for @NoLabelsOrg and @USChamber. pic.twitter.com/Hja42eCKWP
— People for Bernie (@People4Bernie) August 24, 2021