How did St. Stephen of Hungary become a saint?

St. Stephen the Protomartyr of the Christian Faith, became a Saint due to his martyrdom, and he was canonized at the time, as Christians themselves by popular acclamation canonized a Saint, which was...

Saint Elizabeth became a saint because she donated a lot of her money to the poor. She built houses, and founded a lot of hospitals and helped a lot of helpless children, especially orphans.

There seems to be no Saint Cadog, however there is Saint Cadoc of Llancarvan. Is this who you were referring to?

We do not know much aboyt Lydia except that she was apparently the first convert of St. Paul. Evidently she lived a life of heroic virtue as the early Christian community declared her to be a saint...

There are a number of saints named Isidore. Which saint were you referring to?