They wanted HRC to run against DJT because they weren't sure she would win against a traditional Republican candidate. The diluted the Republican vote in the primary split across 17 candidates to make sure Trump would win. Let him have the media coverage etc. expecting to ultimately crush him. Meanwhile there were only 2 candidates vying for the Democrat nomination and they actually had to steal it from Bernie.
They thought she would be the "seasoned" politician vs. Trump's loose cannon.
BOOM!