What groups of St Jerome blamed the destruction of the Roman Empire

Incursions of bands of Barbarians

Explanation:

The most straightforward theory for Western Rome's collapse pins the fall on a string of military losses sustained against outside forces. Rome had tangled with Germanic tribes for centuries, but by the 300s “barbarian” groups like the Goths had encroached beyond the Empire's borders.

the answer is migration

he did it to save us from our sins, so we can see him in heaven 1 day. it's because he loves us so much. he used himself as the final sacrifice, so that we could be forgiven for our sins, so that we can see him in heaven, if we believe.