Moses has persuaded the LORD not to destroy the people and start over with Moses, but there’s still the problem of the people “running wild (for Aaron had let them run wild, to the derision of their enemies).” Moses has to ask for volunteers to salvage the situation; the Levites step up; the seriousness of the situation is reflected in the death toll.
The bigger problem: with the treaty torn up (the tablets broken, v.19), do the LORD and the people have a future, and on what basis? When Moses returns to the LORD to plead for forgiveness, the divine response is two-fold: a command to lead the people to the Land accompanied by an “angel.” Not by the LORD? All the instructions regarding the tabernacle and the priesthood (chapters 25-31): are they all now moot? The plague of unspecified severity (v.34, omitted, oddly, by the Lectionary) seems almost an afterthought.
Looking back over the whole chapter, what advice would we have given Aaron, with Moses off stage for who knows how long and the people expressing real needs? Or we can flip the question. Followers’ expectations constrain their leaders. When do our expectations place our leaders in Aaron’s situation?