There are many phrases of the form
a/n X of Y's
(where X is a term denoting the group of which the Y's are members). X is called a collective noun.
Sometimes, X is 'banal', often applying to many different Y's: a crowd of people; a group of trees.
Sometimes, X is esoteric, usually restricted to one particular Y: a pride of lions; a gaggle of geese.
Sometimes, X is more than just a term for 'a collection of',
indicating more detail about the collection: a flight of aircraft; an
assortment of buttons.
In all these cases, in 'British English', the 'rule' governing agreement is:
Are you considering the collection as a grouped unit
(the team was founded in 1845) (the crowd was the largest ever seen in Michel Delving)
or are you considering the individual members?
(the team were fighting amongst themselves) (the crowd were getting more violent)
In this particular case, I'd shy away from pairing 'people' with 'assortment' (which I feel connotes physical sorting). 'Selection' seems more appropriate.