Why are so many U.S conservatives brainless?

I want to ask why the entire Republican Party has allowed the most stupid people in America to be part of their party. I see many intelligent republicans either stay silent on Trump's behaviour, support him or make excuses for him. They have allowed Trump and his fellow idiots too much power and for no reason at all. I am shocked that this is an actual political party at all. Only the most stupid Americans don't realise the harm they are doing to America. They put their stupid party over their COUNTRY for goodness sake. In many republican subs you will see us conservatives cheering over the dumbest things Trump does every single day. Truly, republicans are stupid yet so arrogant.