The idea is that if their salary does not actually cover the expenses of living in and traveling to DC to do their job, you are limiting the pool of potential congressional representatives to those who are independently wealthy or who are finding other ways to make money via their position.
Paying enough to cover the expenses of the job isn't a solution to all problems, just kind of a minimum bar if we want a normal person to be able do the job without relying on other income sources.
It's an interesting idea. Is that what's happening? The article doesn't suggest it. People like Richard Burr, Chris Collins or Nancy Pelosi were certainly wealthy enough cover these expenses. It didn't stop them from seeking other ways to make money via their position. If your goal is to stop insider trading, you should focus on stopping insider trading.
If your goal is to make it easier to travel to and live in DC, well, congress has the power to address housing (especially in DC) and airline costs for all Americans.
At first I am sympathetic to this idea, but the act of running is so expensive and time consuming, it does not matter what the salary will be, the pool is already limited.
You need to be well connected and/or wealthy before you even start.