they earn more because they put more effort. But in terms of dollar per effort, it only works so well until it hits some ceiling and bottleneck.
Earning power has a more direct relationship with sales, rent and interest, which in most case depends on the randomness of the economy, many other factors etc, but less direct relationship with direct effort and time spent on working. It has a greater relationship with investment, financial information and understanding what is going on in the economy and how other people spend their money.
Te strengthsis defined is work, deadlines and goals, and forcing yourself to reach these goals and external parameters. These kind of milestones work well in terms of self discipline and meeting external demands, but when pushed to the extreme, is OCPD. (i honestly cannot think of another disorder that correlates with this). Also working hard is different from Malcolm gladwell's 1000 hrs of practice theory, which makes you more competent in a skill per se.
One can argue that the top ivy leauge graduates are ENTJs, because it has a direct relationship with working hard, but the top ivy league graduates aren't the top earners, they may be part of the 1%, but they are still not the top earners. Mostly because they don't think about what they learn and how it works in society.
Also INTPs, given motivated enough, will find the laziest approach to making money, which is why i can say a fair amount of INTPs are billionares, but that only when they have enough motivation and can overcome their self doubt.