Not at all. The disagreement was over the use of the word "homoousious" (since it was not used in Scripture) but already agreed with the concept in conveyed... and the Arian heresy. There is no question that they already believed the concepts that became part of the Nicene creed.
Nicea was NOT where we first find that Christ is God. Christ took care of that personally.
Some did, some didn't. That's the point. Before the Church formally declares a dogma, it is not binding on the faithful. Those who did not were wrong, for sure. But there is a difference between being in error prior to a formal declaration, and persisting in error afterward. One is a mistake, the other a sin.
SD
Sure there is a question. Those that believed in the deity of Jesus at the counsel were in the minority.