I'm not countering anything other than to say the common factors throughout all of biology that would help things be larger is the subject. I don't agree that more lift would equal more size and I certainly do not see that in anyone else's discussion. Might have smaller wings because biology will not necessarily grow things bigger than needed. That would be wasted energy. The why, might just be the simplicity that bigger is better in general survival math. If you're bigger you fit in less mouths, if you're bigger and must rival with other males; you win the game of passing on your genes. If you're bigger you can also select from more prey as well as fight off competition easier. Perhaps those are several of the why's of why organisms try to be big.