What happened to the Republican Party I knew?

This is not a settled issue in the Republican Party, and when they set their platform at the Convention, I expect it to be a contested plank. What to do with illegal residents currently in the United States divides many.
Personally, I think denying government benefits would solve the problem on the supply end.

I do weep for the Republican party, as my three favorite presidents of all time were Republicans: Abraham Lincoln, Theodore Roosevelt, and Dwight D. Eisenhower. I place the beginning of the fall of the Republican party somewhere between Nixon's and Reagan's administration. Whether it be their courting of the Evangelical Right, the starting of the war on drugs, or the introduction of trickle-down economics. The point is, somewhere along the line the Republican party ceased being for small and limited government. They got into peoples personal lives, started being for excessive military spending, and overall got away from their more libertarian roots.

Thankfully, libertarian is becoming more popular, in fact the Libertarian party might even eventually become a major party, drawing from both libertarian republicans and libertarian democrats as more and more people become fed up with the status quo.

"Reagan's Amnesty" was a compromise. The Republicans wanted the secure borders. The Democrats wanted more voters on their roles. They compromised. The Democrats got their voters, but the Republicans didn't get their secure borders. That's the nature of compromise. You surrender your principles and get nothing in return.

Look at the Missouri Compromise. The Abolitionists wanted to halt the spread of slavery. The Democrats wanted to expand their "peculiar institution". They compromised and slavery continued. Only when the Abolitionists formed the Republican Party and stood by their principles was slavery ended, but the Democrats hung onto their "peculiar institution" without the chains. First with the Jim Crow laws, then with Johnson's Great Society. Thus blacks remain enslaved to this day. That too is the nature of compromise.

Now it seems that the GOP has become so accustomed to abandoning their principles they have joined the Democrats. Neither party has any principles. They have only ambition to take and keep power.

Who allowed this? We the People. We even encourage it. Who can change it? We the People. No one else.