I think a lot of people underestimate the negative consequences of everyone hating you. The POTUS isn’t a dictator, at least he shouldn’t be, so for someone who proclaims his strict adherence to the constitution (when convenient anyway) I think Cruz couldn’t get much of anything done...well at least nothing that he’s running on.
I think a lot of people here underestimate the negative consequences of voting for someone who's lying to you to get what he wants. Trump may be a born-again conservative. Or he may be a liberal posing as a conservative to win an election. Like Obamacare, you have to vote for him to find out what he's really planning.
Why would Trump go through this kind of trouble? Why did Bloomberg spend hundreds of millions to become NYC mayor? Because it's the presidency - it's a chance to enter the history books. Nobody's ever heard of the 50th richest real estate investor in King Sargon's Assyria. Anyone who's ever covered ancient Near Eastern history has heard of Sargon.