Why would our president want to close our border to immigrants?

After all our country is now made up almost entirely of immigrants, all of whose ancestors have come here during the past 500 years or so, including the ancestors of the President whose grandfather Frederick came here from Kallstadt in the Kingdom of Bavaria at age 16 in 1885, illegally.
So why would this President be now so against others coming here as his own family did, not even 200 years ago? Why does he refuse to accept that that’s who and what we are, a country of immigrants? Why does he not accept that the greatness of our country, that which he would restore, or in his own words make great again, stems by and large from the accomplishments of immigrants most of whom were either brought here enslaved or came themselves illegally, probably without the proper permissions, much as those who are now crossing our southern border?
What’s happening today goes against the grain of what we are as a country. Now the President would remove the TPS or temporary protected status of hundreds of thousands of immigrants from countries close to our Southern border, from Honduras, El Salvador, Haiti, Nicaragua, or from the chaotic Middle East, from Somalia, the Sudan, Syria and Yemen.
Now these so-called TPS immigrants are mostly refugees from brutal authoritarian governments, from civil wars, from natural disasters, and such, and have come here in great need. Why would we not change the “temporary” to “permanent” status? What are we afraid of? By helping themselves to have a better life they are going to help us all to have a better country. This has been proved over and over again.
White House Chief of Staff John Kelly, who If he speaks at all is usually speaking for the President, had this to say in response to an NPR questioner: “The TPS people are overwhelmingly rural people. They don’t speak English … They don’t integrate well. They don’t have skills. While they are not bad people they’re also not people that would easily assimilate into modern American society.”
Now John, and yes, Donald Trump, wouldn’t you agree that your own ancestors were probably rural people and would have faced daunting challenges to assimilation, to finding their own places in our country? Why do you, John, now refuse to accept these new immigrants, probably no different from those of the past, from those of your own past in Ireland?
(I take the following text from a New Yorker article — The Battle inside the Trump Administration over TPS.)
The new Secretary of Homeland Security, DHS, Kirstjen Nielsen, a protégée of Kelly’s, cancelled T.P.S. for the Hondurans…. Given Nielsen’s closeness to Kelly, there was little surprise when she decided to end the protections…. In the weeks before Nielsen cancelled T.P.S. for Hondurans, she had spoken out about a “crisis” at the border, involving a caravan of fifteen hundred Central American migrants travelling north, through Mexico, to seek asylum in the U.S. A Fox News broadcast brought the migrants—almost all of whom were Honduran—to the attention of the President, who immediately began fulminating against U.S. immigration laws. (They were “pathetic” and riddled with “loopholes,” he said.) …
The President, however, apparently didn’t think that his Administration was doing enough. On Thursday, the Times reported that Nielsen had considered resigning this week after Trump berated her in a Cabinet meeting. “Why don’t you have solutions?” he asked her, according to a subsequent article in the Post. He demanded to know why migrants were still streaming north, to the border, adding, “We need to shut it down. We’re closed.”