I watched Channel 4 news last night, and saw Truss being interviewed by Gary Gibbon and she did not come across as someone who is strong and in control of the 'job in hand' (as they like to repeat over and over).
Admittedly I'm not a fan, but she seemed completely and utterly knackered, and not alert /on the ball, as you might expect of the prime minister being interviewed on national TV.
My takeaway from the interview was that the job is simply too big for her, and she is incapable.