His location is not the issue. He traveled nearly openly because to kill him would be a demand for open war.
> Trump was advised that it was now or never if he wanted to make a huge statement
He's tweeted about why he wanted to do it:
https://twitter.com/realDonaldTrump/status/38292347815791001...
https://twitter.com/realDonaldTrump/status/25578456090477363...
https://twitter.com/realDonaldTrump/status/14160455485582540...
I would imagine that the intelligence agencies frequently know where targets are, but only rarely carry out a strike.