I do NOT think that Calvin believed that the apostles wrote the creed. What proof is there? At any rate, his power in Geneva was restricted. I am not a revisionist historian!
The point should also be made that even though Calvin's liturgy included the singing of the Creed we do not know if he championed it for as you say "his power in Geneva was restricted". It is noticeable that other than the Creed Calvin sang nothing other than inspired writings which would establish a
prima facie case but as for 'hard' evidence I will get back to you.
Well after a little digging here is Calvin:
It is most consolatory to think, that judgment is vested in him who has already destined us to share with him in the honour of judgment (Mat_19:28); so far is it from being true, that he will ascend the judgment-seat for our condemnation. How could a most merciful prince destroy his own people? how could the head disperse its own members? how could the advocate condemn his clients? For if the Apostle, when contemplating the interposition of Christ, is bold to exclaim, “Who is he that condemneth?” (Rom_8:33), much more certain is it that Christ, the intercessor, will not condemn those whom he has admitted to his protection. It certainly gives no small security, that we shall be sisted at no other tribunal than that of our Redeemer, from whom salvation is to be expected; and that he who in the Gospel now promises eternal blessedness, will then as judge ratify his promise. The end for which the Father has honoured the Son by committing all judgment to him (John 5:22), was to pacify the consciences of his people when alarmed at the thought of judgment. Hitherto I have followed the order of the Apostles’ Creed, because it states the leading articles of redemption in a few words, and may thus serve as a tablet in which the points of Christian doctrine, most deserving of attention, are brought separately and distinctly before us. I call it the Apostles’ Creed, though I am by no means solicitous as to its authorship. The general consent of ancient writers certainly does ascribe it to the Apostles, either because they imagined it was written and published by them for common use, or because they thought it right to give the sanction of such authority to a compendium faithfully drawn up from the doctrine delivered by their hands. I have no doubt, that, from the very commencement of the Church, and, therefore, in the very days of the Apostles, it held the place of a public and universally received confession, whatever be the quarter from which it originally proceeded. It is not probable that it was written by some private individual, since it is certain that, from time immemorial, it was deemed of sacred authority by all Christians. The only point of consequence we hold to be incontrovertible, viz., that it gives, in clear and succinct order, a full statement of our faith, and in every thing which it contains is sanctioned by the sure testimony of Scripture. This being understood, it were to no purpose to labour anxiously, or quarrel with any one as to the authorship, unless, indeed, we think it not enough to possess the sure truth of the Holy Spirit, without, at the same time, knowing by whose mouth it was pronounced, or by whose hand it was written. Institutes, Bk2, Ch. 16. Sect. 18
