When did "committee" become a collective noun, and why?

OED (paywalled) records two separate words (OED's n¹ and n²), one deriving from a variant of the other. The standard pronunciations of the two words are different.

With emphasis on the final syllable, 'committee' is recorded earlier, from 1472-3, than 'committee' with emphasis on the next to the last syllable, from 1566. The '-ee' suffix of the earlier word has the more usual sense:

...freely added to English vb.-stems to form nouns, ... those in -ee [denoting] the passive party, in such transactions as are the object of legislative provision.

OED derives the later word from a variant form of the earlier. That variant is shown in the earliest quote recorded, that is,

1566 R. Horne Answeare M. J. Fekenham f. 32v The Iudges seeinge the exclamations and confusion..appointeth a Committy, choosinge foorth of sundry partes a certaine number to goe aside with the Iudges, to make a resolution.

OED remarks that the distinguishing stress pattern of the two words

...is suggested by forms like committy (compare -y suffix⁵) which are attested from the mid 16th cent. (compare quot. 1566 at sense 1a); its origin is uncertain, and may be due to association of the word in senses relating to a group or body of people with classical Latin comitium....

The '-y' suffix, in the sense "suggested by forms like committy", denotes an

office or function, or the persons performing it....

According to the Online Etymology Dictionary, the "group" meaning dates from the 1620s.

It seems fairly natural to extend the meaning from a person to a group to which some responsibility is committed. Not clear why that sense came to dominate. Except there are often job titles for individuals with specific responsibilities so maybe it came to be reserved for groups (eg. engineer vs engineering committee).