It wasn't insider info because it was public and hence, no market manipulation. However, also friends & family were informed on time when to buy with this public announcement. But again, the public could do so too.
The only difference is that his friends & family knew he is dead-serious and bought while the public was still in panic/joke/whatever mode debating a gazillion nuances of tariff theory.
Something we should be aware of the next time he tweets something like this and stop blaming him but better ourselves. This wasn't apparently the first time he announced a significant market event to happen.