Perhaps if you actually read Trump’s positions you would see that he is not promising the moon or suggesting something that cannot be done.
For example, Obamacare. He is advocating opening insurance across state lines so that people can shop for their own insurance for cheaper prices.
Perhaps if you listen to him you would see he is, i.e. promising to ban every Muslim from entering the U.S., promising to replace Obamacare with something much better and much cheaper, promising to renegotiate the Iran deal, promising to create a big, beautiful safe zone in Syria, and on and on. Trump's promises far outnumber his concrete proposals for filling them.
Which indicates that Trump knows nothing about the insurance industry. I live in Missouri. Say I surf the web and find a company that does business in Texas but does not have any current policy holders in my state. Why would I go to them and say I want to buy their policy? Why would they sell me one? I can use my current health insurance at my doctor because she is in their network. The Texas company has no network established in Missouri so the odds are my doctor won't accept them. Because they have a network in Missouri my insurance company has negotiated discounted rates for the services my doctor provides. The Texas company has no network established, so even if my doctor accepted them as my insurance the Texas company would pay the full cost of the work done. And the odds of the Texas company going to the time and expense of establishing the network in Missouri for a single customer is about zero. So shopping across state lines for health insurance is one of those sound great ideas that really isn't an idea at all.