Mr. Collins says he is proposing 1o

Elizabeth because
(1) Elizabeth's personality will displease
Lady Catherine
(2)
Elizabeth has shown her affection for him
(3)
he knows Elizabeth will inherit a lot of money
(4)
as the heir, he feels responsible for the daughters
(5)
he knows that Elizabeth would never marry otherwise

(6) He believes that marrying Elizabeth will increase his social status and standing in society.