I suspect that there are some pretty powerful briefings a new president receives that draw back the veil in such a way that targeted killings and torture seem like the only effective response.
https://www.washingtonpost.com/world/national-security/presi...
Some quotes that kind of confirm what you inferred about Obama:
After one of the briefings in 2008, Obama told a close adviser that it was perhaps one of the most sobering experiences of his life. He said, “I’m inheriting a world that could blow up any minute in half a dozen ways, and I will have some powerful but limited and perhaps even dubious tools to keep it from happening.”
“Events are messy out there,” he said. “At any given moment of the day, there are explosive, tragic, heinous, hazardous things taking place.” He acknowledged that as president it was his responsibility to deal with all these problems. “People are saying, ‘You’re the most powerful person in the world. Why aren’t you doing something about it?’ ”
The following made my hair raise a bit:
Trump will receive a book of options benignly called the “Presidential Decision Handbook.” This top secret/code-word book, known as the “Black Book,” of about 75 pages has separate contingency plans for using nuclear weapons against potential adversaries such as Russia and China. ... Two officials said that the “Black Book” also includes estimates on the number of casualties for each of the main options that run into the millions, and in some cases over 100 million.
A man who habitually gets into 3am Twitter fights will command choices that can result in the near-instant death of 100+ million people. That's way more than Hitler, Stalin and Mao managed to kill all together. It's a strange world.