Thread:MJLogan95/@comment-1158537-20190502232540/@comment-2106279-20190502233735

Russo Brothers already explained this. He jumped into an alternate timeline 1940s & lived a life with Peggy Carter. After a long time (after Peggy's death) he took the shield from the alternate timeline (since the original timeline shield was broken by Thanos) and jumped back to 2023.