It's timing more than anything in my opinion
Poch got "lucky" with us, a mostly young and hungry team with a ridiculous amount of talent (prime Lloris, Toby, Jan, Rose, Walker, Dembele, Eriksen, plus Kane, Dele, Son with cameo seasons from Trippier, Wanyama and Dier)
Redknapp also had some pretty fudging decent talent as well ..
Right place, right time. right situation .. look at Pep, how much more resources can a top manager get and fail to win CL again (it was 11 fudging years ago at Barca)
I disagree with Poch over achieving, Redknapp achieved top 4, twice .. Poch overachieving would have actually been winning something, converting one of the many QF/SF/Finals into something .. always came up short ..