Your first question about why people voted for Trump is a very complicated question to answer. I'll try to list a few of the reasons.
1. Some of Trump's voters are die-hard Republicans. They vote for the Republican on the ticket no matter what.
2. Some people voted for him because they like the very things that make me sick. He acts out their fantasies. The misogynists, racists, homophobes, xenophobes, and bullies were thrilled to have a candidate that unabashedly expressed the views they used to have to keep private.
3. Some of Trump's voters did not have a very clear picture of who he was. He starred in a reality TV show where he played a successful businessman. People thought he was the character he played.
4. Some people have very negative views about government. Trump promised radical change, and that appealed to some people.
5. Russia interfered in the election to help Donald Trump. It is being investigated by Special Counsel Robert Mueller. Social media was hijacked to exploit differences among Americans and to spread ugly false rumors about Hillary Clinton. There have already been 20 indictments and five guilty pleas for crimes related to this, and it is only the first year.
6. Hillary Clinton is not a good campaigner. She also took "the high road" and never tried to match Trump insult for insult. It made her seem weak, but it actually takes tremendous strength to keep your cool and stay out of the gutter. Hillary also likes to play it safe; she was afraid that if she hit back too hard, she would look like a shrew. It was a classic case of "damned if you do, damned if you don't."
7. The ridiculous email scandal hurt Hillary. The FBI investigation showed that no crimes were committed, but James Comey broke the rules and publicly smeared Hillary. Bernie Sanders also smeared Hillary about the money she earned for speeches. She did nothing illegal, and the payments she received were in line with what other former Secretaries of State received. Far from being crooked, Hillary was one of the most honest people ever to run for president.
8. Lastly, the outdated Electoral College tilted the election to Trump. If a total of 78,000 votes in three key states had gone the other way, Hillary would be president. Also, bear in mind, she won 3 million more votes than Trump, so American voters actually preferred Hillary.
Now to your second question about the Democratic response. You seem to think that the Democrats are not rebuking Trump which is entirely untrue. They are all but screaming their objections from the rooftops. I don't see what more they could be doing. Keep in mind Republicans are in control of Congress. Your question should be, "Why aren't Republicans rebuking him?"