You get what you measure (and reward)
It's very simple really. More or less any unelected group, provided they were reasonably well educated, intelligent, and of inquiring mind, would do better than the House of Commons. Why? Because they get there by being elected, so that's what's bound to be on their minds most of the time.
Plato pointed this out in "The Republic" (fascist as it gets later on). What sort of person would we prefer to be ruled by? he asks. Clearly, the sort of person who does not want to rule, has no intention of running for office, and would refuse if invited.
For millennia, the ordinary people ("citizens") have been fairly lucky in that their rulers were pretty amateur in their approach. Roman emperors, for example, typically spent a few years leading armies in the field, or lolling around eating nightingales' tongues and having orgies, before taking over a post in which everyone told them they were doing a great job (until they were assassinated). What chance did they have of running things efficiently? Two centuries ago, or even one century, most British MPs had useful (or at least lucrative) other lives, as doctors, lawyers, soldiers and sailors, merchants, etc.
Nowadays, a few thousand years into the game, politicians have finally done what would have taken a more competent bunch a few years at most. They have started applying state-of-the-art know-how to getting what they want - namely, getting elected, staying elected, avoiding any undue work or career risks, and making the populace shut up and do what it's told. Where did they learn all this? Basically, by copying business - they have adopted spin, PR, marketing, advertising, and above all the common approach that underlies all of these - lying.