I think it's because it's one thing he can control all by himself. Look at all the attention he's receiving. The "will he/won't he" reality TV. Put a tweet saying X%. No, they won't be cancelled. Yes I'm suspending them for 90 days. And so on.
There were a bunch of sentences regarding non delegation of powers of congress, mainly for federal agencies, and courts deciding that congress can't delegate those faculties, so, by the book, this would be a similar situation. There is actually an ongoing case for this aspect of the discussion:
https://www.theguardian.com/us-news/2025/apr/07/trump-tariff...
even then, congress can vote but who would actually remove him from power?