My Latin-Dutch dictionary (Muller-Renkema, 1970) lists the debauchery, without the macron, as first lemma, saying it’s related to lŭtum, mud.
The sacrifice, with the macron, is related to lūstro, which in itself has two meanings.
illuminate, derived from a reconstructed form leuk-s-trom
purify, derived from a reconstructed form lŏu(e)s-trom cf. ἐ-λοϜεσ-σα ...