I'd have to guess this manufactured drama was agreed/requested by Trump, so that he can act the hero by making a "deal" to get it unblocked tomorrow or soon after.
The real question here is "What's in it for Trump?". He doesn't do anything without expecting something in return. What is Trump personally getting out of (about to) letting TikTok continue?
There's always the basic drives that his mental illness place in his actions. If nothing else, attention, validation and social status are plenty enough for someone of his condition, that of narcissism.