President Trump is a serial liar. In fact, he averages 13 lies a day. So when he says he was honestly working to end corruption in Ukraine by withholding military aid as leverage, he's probably lying. The guy seriously makes things up just because he can.
The Washington Post has a database of every single lie from Trump. At last count, Trump has said 13,435 lies over 993 days.
Despite the evidence and testimony, many Trump supporters are sticking by him. They repeatedly refer to a debunked conspiracy theory that says Ukraine was involved with hacking the Democratic National Committee in 2016.
Another argument is that nothing actually happened. There was no conspiracy or organized effort from the Trump administration to pursue those goals. Trump goes off-script fairly often—Democrats are making things bigger than they really are.
They take Trump at his word when he says he did not want anything from Ukraine.