The preposition for seems strange here. One wonders if the for might be an error for some other preposition. The phrase here seems to mean ‘because of the multitude’ or ‘given the multitude’. Interestingly, usage like this is found in the King James Bible. In fact, there is one involving multitude:
Three biblical examples involve the word press, which had the meaning ‘crowd’ or ‘multitude of people’ in Early Modern English:
The Oxford English Dictionary lists this use under definition 22 of the preposition for. In other words, 3 Nephi 17:10 states that although everyone was able to come forth and bow down before Jesus, there were limits to how many could kiss his feet (due to the size of the crowd). The critical text will retain the preposition for in the phrase “for the multitude” since it works textually.
Summary: Maintain in 3 Nephi 17:10 the preposition for that occurs in the phrase “for the multitude”; such usage is found in the King James Bible and means ‘because of the multitude’ or ‘given the multitude’.