The Pope can issue what he wishes to issue if he so decides. But the episcopate is a collegial institution and the Pope often will (and did in the two instances I referenced) work in union with the other bishops.
If the Holy Spirit is leading them, it had better be unanimous.
I'll bookmark this comment for later reference when you or someone else says that "Bible Christians" require no Magisterium because the Holy Spirit leads them. I trust you'll apply the same standard of unanimity then, right?
Iirc, there was unanimity on the doctrines themselves, just a few voices (John Henry Newman being one notable) who cautioned against issuing the formal definition at that particular point in time.
So how does this happen?
There are books and other resources out there if you're genuinely interested in knowing the times and circumstances that have led to the Church making formal definitions of doctrine. For some topics, the pithy 2-sentence answer you seem to expect isn't possible. So how does this happen?
Is the pope elected by unanimous vote or majority vote?
Maybe you'll get the point then.
Catholics try to disqualify SS because of lack of uniform or unanimous interpretation and yet when it comes to their own magisterium, they are willing to allow for non unanimity.
IOW, it doesn't HAVE to be unanimous. It's a double standard.
That's hypocrisy, plain and simple.
If Catholics and Catholicism allow for non unanimous decisions to be made by their magisterium and still consider it to be led by the Holy Spirit, then the same standards ought to be applied to EVERYONE.
Non-Catholics should not be bound by standards Catholics don't even apply to themselves.
As soon as you can prove that all Christians are at the same stage of spiritual growth. Or perhaps you can show that any Protestant claims they are the only "church" and all must believe as they do and be subject to them. Can you show those things?