Why did many people seek from priests as the black death spread through europe?

The Church was the trusted society that everybody knew. Almost a safety net, the Church was involved in every important part of the people's lives. When the Black Death spread through Europe, people fell back on the Church because they thought the plague was a punishment from God and the people wanted to know what they could do to stay safe. The Church doled out penances, or tasks the people had to complete that would appease God. As we can tell from history, the Black Death swept through no matter what the people did, and the Church lost the favor of the people when half of Europe's population died.
Hope this helps,
Ahawk