The Twitter rebrand from a recognisable blue bird to a generic X is happening in real time in full view of, well, everyone. Usually rebrands take months, if not years. They happen behind closed doors and are cooked until ready, but Elon Musk is making tweaks to the X logo in public on a whim as the urge takes him. It's like branding doesn't matter anymore.
Following the controversial removal of the little blue bird in favour of an X logo, causing designers to roast the Twitter rebrand, it seems Musk wasn't satisfied. He momentarily changed the X logo, perhaps after someone pointed out that it already existed as a Unicode character. The new X design was similar but had slightly thicker lines. But within hours Musk had decided he didn't like how it looked so he had it changed back again.
