Chrysalis is between a rock and a hard place, on one hoof she has Equestria that could keep her subjects alive and happy for years but cannot conquer it. On the other she has a race of changelings to feed so how do you feed your children? The Changeling queen is not above her subjects but will do anything for them...even give up her castle and everything to keep her subjects alive and how do you do that. Only Infultrate equestria so you can use what you know about love to make happy couples and further increase the output of love. Ya nothing can go wrong with this plan...especially if she chooses her main headquarters to be in ponyville.