In October of 1978 Karol Wojtyla was elected pope out of 111 voting Cardinals; remember that Cardinal Siri (Siri Thesis) was still living and participated in the conclave. Siri did not die until 1989.  Of the 111 Cardinals, all of them (save three: Baum, Corneliano, and Ciappi) were consecrated bishops prior to 1968.  So that makes 108 valid bishops; now, a sizeable number of them were appointed as cardinals in the 1970's.  I realize that the majority of Sede's will argue that these valid bishops were not cardinals, therefore no valid papal election. 

And Cardinal Ottaviani (the Ottaviani Intervention) was made a cardinal-deacon by Pope Pius XII, but was not consecrated a bishop until April of 1962 by Pope John XIII.  Ottaviani could not vote in the 1978 Conclave.  So I guess some will hold that Ottaviani was a valid cardinal because he was appointed by Pius XII, but he was a question mark as Proto-Prefect of the Doctrine of the Faith.   

How is any of this relevant?

Fifteen valid cardinals unanimously elected an antipope during the great western schism.

No amount of bishops can elect a heretic.

I agree. I don't know about Siri, Ottaviani, the number of cardinals that were actual bishops, etc.... the fact of the matter is that John Paul II was a heretic and an extremely public one.

Also, why does it matter the validity of the episcopacy of cardinals? Throughout history you've had even deacons who have been cardinals (not exactly the same as cardinal-deacon). Pope Gregory XVI was a presbyter when elected to the papacy (was previously a cardinal), John Henry Cardinal Newman was never a bishop, there was a Pope in the 9th century (?) who was elected to the papacy and died a deacon a few days later without even receiving the priestly order.

In any case, what matters is the validity of the Pope that created them cardinals.

I realize that the majority of Sede's will argue that these valid bishops were not cardinals, therefore no valid papal election.

What you might want to consider realizing/learning is that you have very little idea or understanding about what others will think, argue, reply, etc. -- whether the subject matter is V2 or fine wine or football.  Just ask your question and leave it at that, actually allowing others to answer for themselves.

Traddieland has suffered tremendously from those who, while pontificating about what they (presently) know to be true, erroneously believe they know the thoughts and beliefs of those with whom they disagree.

If the Siri thesis is false, JP2 could have been elected validly (per the conclave changes by both St Pius X and Pius XII) and been a "materially/govt/human aspect" valid pope.  All of the spiritual penalties he incurred before his election (due to his unorthodox opinions, actions, etc) would immediately go into force, the second the conclave was over.  Thus, JP2 would've been 'spiritually impounded' (to use Fr Chazal's phrase) and have no spiritual authority due to heresy/excommunications, etc.  Added to these excommunications (if such is possible) would be all the numerous, scandalous, sacrilegeous, blasphemous actions he did AFTER the election, and his status as a 'heretic' is unquestionable.

We all hope he repented before death, but based on exterior evidence only, JP2 will go down as one of the most horribly anti-catholic popes in history....even if he held the material office.