It is not known whether the officials that we put into office will make good on their promises and do things for the good of the country. When we elect people into office we have to take that risk. There is a chance that they will try to do well for the people but it may be difficult.
No, Trump's appointee will not keep the interests of the American people in mind. The American people will come second to corporations for the next four years. All of Trump's men want to make a profit, and this is the perfect way to do it. They will ruin the economy to benefit themselves.
No, Trump's appointee to the treasury secretary position will not likely keep the interests of the American people in mind. Like Trump's other appointees, he will likely advance the interests of Trump and his buddies--both the wealthy businessmen and the racist alt-righters. The rest of us will have to take the leftovers.
Trumps appointee to the Treasury only has his own best interests in mind. This is true for everyone involved in the presidential election and it will have terrible consequences for the American people. More people will lose their homes and their pensions, and people will die as a result of his policies.