I think it's because Hull FC, under Radford, are far too inconsistent. Massive defeats, massive victories and everything else in between. Whilst you can win a cup competition in this way, you can't expect to finish high enough in a league format to have a good tilt at winning a Grand Final.
Under Powell, Cas are pretty consistent. Cas don't ever seem to go on a 'bad run' and lose a string of games like Hull do (eleven loses in a row at the end of 2018, and one win from the last 7 games of the season in 2019). Runs like that suggest Radford cannot turn around a losing team, at least not until the following season! Compare that to Cas, who in the last three seasons have never lost more than two league games in a row, and I think you see one reason why people question Radford more than Powell as a coach.
Radford cannot get his team playing consistently, and he can't turn things around when the team is under-performing. Powell can, and it's why Cas have been in the play-offs consistently whilst Hull have not. And that consistency is also why Cas have finished above Hull for five of the six seasons the two coaches have been at their respective clubs. So to answer your question, that record is why people mention Radford as the reason Hull might not do as well as expected, whilst not many think the same about Powell.

Yeah but Cas fans don`t constantly moan about Powell do they? Different club, different set of expectations (Historically, although they are probably now a lot closer than they once were). Sorry to say it but the conception of Radford comes from within your own fan base...

Powell turned a team of nobody's into a top 4 team. Even little Cas are. Still a top 4 team since 2016 or so. Yeh we bottled the GF but apart from that we don't really lose the big games. Having beat Saints in the 2017 semi final.

Where as Radford should be doing much better with his squad and facilities but just isn't. Apart from doing OK in the CC.

St Helens
Wigan
Castleford
Salford
Hull
Warrington
Leeds
Huddersfield
Catalan
Toronto
Hull KR
Wakefield

I can honestly say that as a Hull fan, I agree wholeheartedly with your post. The inconsistency within our team has been a source of great frustration for a few years now and when you have a coach that openly admits that he doesn't know how to get the best out of his players, then where do you go from there??

I think we do underperform in big games.
2014 Challenge cup final.
2017 Grand Final (and let’s remember how lucky we were to beat St Helens in the semi-final too).
2018 semi-final at Wigan. We were nilled. Never looked like scoring.
2019 play-off game against Salford. Again, nilled. Again, never looked like scoring.

We do lose the big games.

He's done better than OK, but for some b2b Challenge Cups at Wembley cloud their view of just how good a squad he had, and has for this coming season. Too many FC fans would see a top 5 finish as success. The majority, however, believe we will challenge this season, every team has cheerleaders and doom mongers.

So has Radford, he took over a average side and won us two major trophies with 4 years. He has made mistakes recruitment wise, but seems to have learned from that, think our best signing in the off season could be Purtill, think an experienced assistant is exactly what Radford needed.

Dont Cas spend the same as Hull, so dont get your point, our facilities are good, but financially work against us.

Clearwing leads the way with an intelligent analysis and most agree.....Picked this one out as it is very telling when it comes to the possibility SL will go to 10 at some point. Certainly not to 14 again. Worth remembering next time some people start constructing fantasy leagues.

In the previous thread we had for 2020 predictions. I’m sure I had Wakefield second bottom. However, in light of the injury crisis they are going through (even though the season hasn’t even started!!!) I would like to revise my prediction and put them bottom

i’m gonna go;

St Helens
Warrington
Wigan
Leeds
Hull
Catalan
Castleford
Wakefield
Huddersfield
Salford
Toronto
Hull KR

You are nothing if not predictable.

We already have about 8/9 players out injured. I would like to revise my prediction and take us out of the top 5 and put us about 9th

Its a joke now.

It does make you wonder whether too much is being asked of the players.
More and more games and the international program or World cup, at the end of each season, meaning a very short off season for so many players.
It's no wonder that so many are busted
It's certainly time for the Easter fixtures to be changed but, I'm sure that we'll get back to that one nearer the time.

It does seem that more and more clubs are getting more and more injuries