We adore You, O Christ, and we bless You,
Because by Your Holy Cross You have redeemed the world.
In the past when I've said the prayer, I have considered both "adoration" and "blessing" to be consequences of the Redemption. Because of the Redemption we both adore and bless Christ.
It occurs to me, however, that adoration and blessing (or praise) are not the same thing. While we may praise or bless God because of a particular benefit, such as the Redemption, the reason we adore is simply because God is God. No other reason. "Adoration belongs by right to the Lamb who was slain" not primarily because he is the Lamb that was slain, but because He is God!
For this reason I have taken to praying the prayer like this:
We adore, O Christ,
And we bless You because by your Holy Cross You have redeemed the world.
I have no idea how St. Francis punctuated it in the original, if he punctuated it at all, but this makes the most sense to me.