Speculation:

Trump was under investigation for national security violations of colluding with Russians to influence the 2016 election. What if a FISA was put on Trump? Would FISA judges go for that? They would be on that like white on rice, no?

And who did Trump talk to? Everybody. And everybody talked to everybody else. With 2 FISA jumps, you have legal authorization to listen in on just about everybody in the world who might be involved in mischief.

Chess move?