关于notleast
请教关于此句中notleast的用法:Tosuchmotives,yetanothermustbeadded.Thecontemporaryphenomenonofcarworshipistobeexplainednotleastbythesenseofindependenceandfreedomthatownershipentails.Tothispleasurecampinggivesanexquisiterefinement.
此句中notleast它在句中是什么作用?作什么句子成份呢?