Helmut Zemo is a former soldier from Sokovia, who wanted to avenge his family’s death during the Sokovia incident. He wanted to do this by destroying the Avengers, but knowing he was just a man going up against superpowered people, he had to be smart about it.
And that’s the thing, Zemo is really very smart and a brilliant strategist and manipulator. He’s patient, knows how to put a plan together and stick to it, while using the latest developments in the world e.g. the Sokovia Accords, to his advantage.
You could say that Zemo’s plan wouldn’t have been as affective if Steve had told Tony about his parents’ death before being forced to watch the footage of it. if Tony had known there’s probably less chance of him flying off the handle. But Steve didn’t tell Tony, and Zemo’s plan to destroy the Avengers worked.
I think Zemo was a brilliant villain and he’s one that actually achieved what he set out to do. He destroyed the Avengers by turning the two main leaders of the team against one another. He broke the Avenger a part. Friendships were destroyed, some members of the Avengers were on the run and wanted by the UN, and the rest were just hurt and alone.
I think he’s a fascinating villain and I’m pleased that he’s still alive. I think he’d be a great villain to make an appearance again at some point in the future. Although, he’s played his best hand with the secrets about Tony’s parents’ death. Unless he’s managed to dig up something else on various members of the Avengers, I’m not sure he would have the same impact. Maybe it’s because I like Daniel Brühl so much so would like to see more of him in the MCU.