The intelligence community has their hands tied when it comes to their own citizens due to strong constitutional protections, so in order to get what they desire, they operate quasi-extrajudicially (i.e. exploit a loophole) where they just get a friendly foreign power to do the spying and then trade intelligence for intelligence on their own citizens. I'm pretty sure this kind of scheme is behind GP's post and such an arrangement is not limited to members of the five eyes.
https://www.theguardian.com/us-news/2015/jul/08/nsa-tapped-g...
https://www.nytimes.com/2015/05/22/world/europe/intelligence...
https://www.huffpost.com/entry/us-spying-angela-merkel_n_416...
Not always; google for 'dancing israelis'
Citation needed. We hear this all the time, but from where I stand it looks like a pretty one-sided "relationship."
We give them billions every year while running a deficit and what do we get from it?
In fact, its well known with the intelligence community that Israel is by far the greatest intelligence now that Communism doesn't exist anymore.
Also the Mossad is working a lot with the secret service in the U.S
I believe there is a deeper reason behind those actions that won't be revealed to us (it can also explain the lack of actions of the U.S towards this case)