Conservative groups influential with the Trump administration have pressed for the preemptive acts of clemency.
There’s a world of difference between a pardon issues to prevent malicious prosecution for non-crimew and one issued to people you’ve been instructing to commit crimes



The president’s power to grant clemency is almost completely unlimited.
So he can’t pardon someone who has been impeached and he can only pardon crimes against the United States, meaning federal crimes. That’s the only limit in the Constitution to his power. The only thing he can’t do according to the Constitution is pardon people who have been impeached and state crimes.
Preempive pardons have been granted in the past. Gerald Ford issued Nixon a “full, free and absolute pardon” for any crimes Nixon might have committed during his presidency. There is no requirement that the crimes pardoned be defined in the pardon. The only rule, per SCOTUS ruling in 1866, is that the crimes be committed prior to the pardon.
Trump has also talked about issuing himself a preemtive pardon and people have argued about whether or not the president can do that. I’m pretty sure I know how this SCOTUS would rule on that if and when it comes up.