Sir Tat did not skillfully catch Katie out, far from it. He, and the people who interviewed her, could see that Katie was clearly too good for the position she was applying for, which was what made them all suspicious. That's why they all had reservations about her, because they knew if she did accept the job, she would only use it as a stepping stone to something far better. Despite these reservations Sir Tat put her through to the final because he knew how capable she was.
Like all the other contestants in beginning, Katie believed she had a good chance of winning the competition, which is why she didn't really think through the implications of moving her family to fit around the job. But once Sir Tat had put her through to the final, she suddenly realised the enormity of the situation, which is why she walked away. To someone like Katie, who loves the challenge and the thrill of the chase, the prize on offer wasn't good enough to warrant her and family uprooting. That is why she walked away.
Whether you love her or hate her, Katie was clearly the most talented and savvy amongst the applicants. She was clever, personable, calm, quick witted, ruthless, professional and driven. The same cannot be said of all the other contestants apart from Lohit. And to me, his firing was the most ridiculous action taken and sums up just how poor Sir Tat's judgement really is.
The show needs to get rid of Sir Tat and his tat companies, and replace him with a respected businessman whose company is a byword for quality - something non of Sir Tat's companies are.