If Cox was using his position as an MP to enrich himself or benefit his business associates by influencing the government, that would be corruption Actually no, that would be influence peddling, which is another game popular among Tory MPs.
Having a second job which pays a high salary is not corruption. It is just not that simple. It depends on the second job and how it was obtained.
We can call it dereliction of duty and be generous, then. How has Cox properly fulfilled his duty to his constituents by buggering off to the BVI for months (to advise their government on - wait for it - defending themselves against corruption charges). At least he is admirably qualified for that role.
The fact is that people like Cox and other rich, white (primarily, not exclusively) men do play by their own rules, as they have invented MP Duty no. 4.
MPs have 3 duties: to the national interest, constituents and then their party, in that order. Not only do many moonlighting Tory MPs put interest no. 3 above no. 2 at every available opportunity in order to secure their own positions and bootlick, but they have also invented MP Duty no. 4: to act in their own personal financial interest while completely ignoring their constituents, about whom they care nothing.
These people may think themselves above the law, but like everyone else they have a 24-hour day, and it's just not possible to give equal commitment to multiple demanding jobs at high levels and perform them all equally well. Rest assured that Cox's priority on any given day during that BVI job was not to listen to Aggrieved from Torridge at an MP surgery. Here's what his constituents think:
www.independent.co.uk/news/uk/home-news/geoffrey-cox-caribbean-second-job-bideford-b1954338.html?r=66454
"Dereliction of duty is a person's purposeful or accidental failure to perform an obligation without a valid excuse, especially an obligation attached to his or her job".
The Guardian lying again, is it?
www.theguardian.com/politics/2021/nov/09/sir-geoffrey-cox-the-infatigueable-rides-to-the-defence-of-tax-haven-against-uk-foreign-office