Did Jainism exist in Satya Yuga?

From Rajat Prabhu:

You mentioned that Jainism developed around the 5th century BC. But Srila Prabhupada says that Jainism existed even in Satya Yuga since the time of King Rishabhadeva. How can we reconcile the two? And if it existed in Satya Yuga, then is it also an contender for being the oldest religion along with Sanatana Dharma?