That's been their problem for a long time though. As a family at best they are average, in some respects below average at some things. They got bigger on youtube when Chris worked an average job, Sarah stayed at home and whilst she still shopped a lot, didn't seem to spend £100 a day at B&M, the kids went to school and did normal every day activities like thousands of other people. Yes they still went on holiday too much but a week in Spain and a weekend at Butlins was still relatable to many people, even if most people didn't do it as frequently as them.
Now she has to say that they are the best at everything to the point where even when everyone knows it's a lie, she can't tell the truth. She's blatantly lied about the marble floor being real - nothing wrong with saying "no it's not real marble, that would be really expensive and we still like the look of the cheaper alternative". Nothing wrong with doing an exam and not getting the very best result. Even with the latest vlog, why say it's the most expensive. The children make best friends in an instant, health visitor thinks Jace is the most intelligent child she ever did see, Esme and Isla were the best at their dance school despite not even attending for weeks.
Bragging about money at a time when most are worried about it is also her desperate need to have people somehow think they are the best, when in their situation most would be in a major panic about where the income will be coming from to pay for increasing costs with an unstable income, a large cold house, large family at home all the time and the need to keep paying for holidays/shopping to impress people.