When Fear the Walking Dead first aired in 2015, it appeared to have been set up for failure. With an entirely new cast of characters in The Walking Dead universe with no connections to the original series, there was concern that fans would have trouble getting attached to this story. The first season followed The Walking Dead's critically acclaimed Season 5 and had high expectations to live up to. While it took a bit to get people on board, there came a time when Fear the Walking Dead became arguably better than the main series.
Source：https://www.cbr.com/fear-the-walking-dead-series-finale-review/
