Mansford is the CEO so he deals mainly with the management of the club i.e. sorting out the paperwork and negotiations with transfer, getting sponsorship deals, engaging the club with the community and on those fronts I would say Mansford has done brilliantly.
He's managed to sign a full squad of quality players for this level before the end of the transfer deadline, gained an incredible number of sponsors that the club otherwise wouldn't have gotten, and re-engaged the community with campaigns such a Backing Blackpool. He's actually done a really good job IMO.
You could probably criticize Johnson more, but I wouldn't put the blame on him either as the players he's recruited have been very good. Garbutt, Grétarsson, Robson, CJ, Keshi, Dougall, are all quality League 1 players and we were lucky to get them in. Yates, Mitchell, and Ekpiteta have shown flashes of being more than good at this level, but think they'll take longer to develop. I think the only player who Johnson's brought in that hasn't quite panned out yet is Lubala, who could still turn out to be a decent player down the line.
Overall, I don't think the blame lies at anyone other than Critchley right now. He's been backed thoroughly and I don't think it's fair at all to blame Mansford or Johnson for the early struggles.