Judges have to be careful with their orders. They have a lot of power, but are always subject to review. No judge wants to see their orders overturned on appeal because of some action they took.

So while a judge absolutely can impose a broad gag order on Trump right away based on his past behavior, his lawyers get to appeal, and they have shown that their legal strategy is whining about every little thing until they get their way.

By doing out punishments in small stages, he can establish a clear pattern of objectionable conduct, such that when the harsher penalties come, his lawyers have a much worse position to whine from.