Yes, it was. 100%. If the North hadn’t wanted to get rid of slavery, the South would never have seceded.
It is a total revisionist myth that the North was against slavery.
Initially intended to express anger at the draft, the protests turned into a race riot, with white rioters, predominantly Irish immigrants,[4] attacking blacks throughout the city. The official death toll was listed at either 119 or 120 individuals. Conditions in the city were such that Major General John E. Wool, commander of the Department of the East, said on July 16 that "Martial law ought to be proclaimed, but I have not a sufficient force to enforce it."[8]New York City draft riots
The riots remain the largest civil and racial insurrection in American history, aside from the Civil War itself.Now tell me again about the myth that the North during the Civil War cared about the plight of Black people.
The North wasn't a monolithic entity, so of of course it wasn't "against slavery" in terms of total unity.
But it's the height of deceit to assert that the abolotionist movement wasn't growing in strength—particularly in the North—in the decades leading up to the Civil War, and it's outright absurd to think that Northern parents would send hundreds of thousands of their young men to die in a Civil War, absent a "righteous cause" to unite them.
By the time the Civil War was well underway, there can be no doubt that the abolition of slavery was that righteous cause, and it's absolutely ridiculous to assert otherwise.
While very few wars are fought over only a single issue or concern, any attempt by Confederate apologists to minimize the importance of maintaining slavery as a Right (in the South), or to dismiss the desire to abolish slavery as a righteous cause (in the North) is patently ludicrous.