Peter probably means here that Christ died in order to create a close relationship between us and God. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "flesh" refers to Christ's body; Christ was physically put to death. This can be stated in active form. Alternate translation: "People put Christ to death physically" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-activepassive]])