At Wednesday's hearing, Rep. Matt Gaetz (R-FL) argued that if President Donald Trump is being impeached for withholding aid to Ukraine, then President Barack Obama should have been impeached for not offering weapons to Ukraine in the first place.
But putting aside the fact that the Obama administration actually did provide some security aid to Ukraine, there was a very clear national security reason why the Obama administration was reluctant to approve lethal force on the same scale as the deal blocked by the Trump administration, as former federal prosecutor Mimi Rocah explained:
Just a reminder @RepMattGaetz that Obama witheld aid to Ukraine because it was still a country led by a corrupt le… https://t.co/tSgCjzfRJC— Mimi Rocah (@Mimi Rocah)1576164274.0
To put it another way, the previous administration's decisions about military aid were in the national interest, whereas Trump's decision to suspend aid until Ukraine investigated his political rivals subordinated the national interest to his personal interest. Which is the heart of the Democratic case for impeachment.