Secret Service Director Kimberly Cheatle, who came under scrutiny for the agency’s failure to prevent the assassination attempt on Donald Trump, has resigned.
She was criticized for failing to prevent the assassination attempt on Trump.
There are legitimate reasons for denying increased security. One of them is the Congressional favorite excuse for things not being done that should be, the budget. If there isn't the budget for increased security, then a denial would be expected. A very vocal portion of Congress loves to talk about their about shrinking the budget all the damned time. One of the consequences of that is not having the budget to react to changing circumstances.
It does, because that's what department heads do, they take the fall in situations like this. Even if the root cause wasn't related to them. It's an expectation of the position.
The response to those shootings was exactly by the book while the response in Trump's case was sheer incompetence. You can't control the shooter, but you can control the readiness and response and those were abysmal this time.
I'm not sure if you saw my edit that tries to clarify this point. The two attacks mentioned had secret service handle things by the book and no one got fired. This time with the Trump attack, was the opposite. Sorry for any confusion.