mysticism kabbalah - The Origins of the Zohar - Why is it accepted as being true?

I've read arguments and counter arguments for the origins of the Zohar and I'm perplexed.

I personally accept the truths in kabbalah and chassidut, but I didn't realize how the Zohar sort of just "appeared" one day in 13th/14th century. Le-havdil, this sounds like how other religions start; with one man claiming to have found an ancient text he won't let anyone else see.

For sure, there are traditional arguments - and even secular academic ones - that paint a better picture of events and present other possibilities for the provenance of the texts of the Zohar.

My question is: With such a shaky story, do we say that Zohar is accepted based on the truth it contains (i.e. regardless of where it is actually stems from) rather than the mesorah (since it apparently doesn't have one)?