high crime explanation

"Daddy, why was the president impeached?"
"He threatened to withhold military aid from a country we shouldn't have been arming in the first place, unless they announced an investigation of a known bent politician from the US. Neither the withholding nor the announcement ultimately happened."
"At school someone said the Democrats didn't want to do any soul-searching about why they lost in '16 and they came up with this instead."
"That's certainly true."