He was well known to some cardinals long before he JPI conclave. He had participated in Vatican II and not as a wallflower and his book on sexuality was well known and respected. His philosophical writings and his work implementing the council in Poland were also known.
He was unknown to the media and to world-illiterate Catholics in the US and Western Europe. But that’s always a good sign, when the low-information Catholics don’t know about someone. Beware the candidate that the LICs know well.
If the LIC’s are even bothering to pay attention at all, period.