>>18092980
It was never a widespread practice among Medieval and Early Moden Christians to begin with. The Church often opposed it (making exceptions for Muslims or Pagans as needed) and Christians themselves had serfs so there was no need for slaves. The only place they were used agriculturally was southern Iberia.
The exceptions you mention are navy related. Galleys were full of them, they were basically the naval war engine for 2000 years in the Mediterranean. And it was one of the worst punishments except for outright torture. In many ways it was outright torture, being chained day and night to a wooden bench and whipped to row. Being fed only thin gruel and pissing and shitting right where you sit and sleep. disease, malnutrition, cold, infections, putrid air etc. Mortality was very high so they had to be constantly replenished with more raids
Millions suffered this fate through the ages.