General Discussion

yet another power grab?"

Here's why.
Reason 1: It's less about a launching a power grab, and more about maintaining the existing illusion of power. He's about dictatorial power spectacle.
The felon launches his most familiar spectacle (from his growing repertoire) that plays to the RW stereotypes re non-whites and crime, that he knows most folks already believe.
Re DC numbers, his spectacle plays to a timeline of the truth getting out in a familiar sequence:
-- after he holds Leavitt pressers that announce arrests (assuming he's not stopped by Judge Breyer over the Posse Comitatus criminal case against him in San Francisco) https://www.democraticunderground.com/132284508) in other blue cities, and
-- then leaves the left and rw press to sort out all their interpretations and predictions of his actions;
-- over time he'll spread more arrest numbers on platforms, then
-- he'll be told the crime numbers in DC (likely in one of his taped WH pressers) are low, at which point
-- he will take credit for those numbers, then
-- spread that taped segment through the rw echo chamber.
Reason 2: Even though the evidence Judge Breyer has against his "inward" use of the US military is solid, Trump will have his DOJ fight to publicly beat this federal judge, while he berates him in public platforms to gain more sympathy votes from anti-crime voters. Even if the judge (and/or SCOTUS) rule in the CA governor's favor, Trump's overall goal will be to ignore the rulings, and continue to turn the US Military inward, in what will amount to his "unitary executive power" challenging to the upper courts to enforce their rulings.
https://www.democracydocket.com/news-alerts/trump-california-national-guard-deployment-trial/