@Health, very good so you realize both under Obama and under Trump money was withheld from Ukraine.
The key difference was in the objective of why they each withheld the money. One did it in accordance with proper US policy the other (Trump) did it for personal benefit. It might surprise you, but a President using his office and demanding investigations into political opponents is not proper US policy, rather that is something that stinks of autocracy and abuse of power. I thought this was pretty clear since the days Nixon was in office.