Saying, We give thee thanks. The only instance in the Apocalypse of the use of this verb. It is found in John 6:11, John 6:23, and John 11:41, but in none of the ether Gospels, though frequently in the Epistles.
"The elders" are peculiarly indebted to God, since the establishment of his kingdom is the victory of the Church. O Lord God Almighty, which art, and wast, and art to come; the Almighty. Omit "and art to come" (Revised Version), with א, A, B, C, P, Andreas, Arethas, Primasius, Syriac, Armenian, etc.
(cf. Revelation 1:4; Revelation 4:8). Perhaps the future is purposely omitted, since God's "coming" is now an accomplished fact (cf. also Revelation 16:5). Because thou hast taken to thee thy great power, and hast reigned; because thou hast taken thy great power, and didst reign (Revised Version).
God never ceased to reign, though for a time he abrogated his power. This power he has now reassumed, and the elders thank him for it, for it is the assurance of the end of the suffering of the Church of God.
So in Revelation 4:11 the elders declare that he is worthy to receive the power which he now visibly exercises. It has, indeed, been exercised before. The preservation of the Church set forth in the visions of the seals, and the punishment of the ungodly shown under the trumpet visions, are effected by means of this power; but now that power is visibly exercised.