It could just be a reflexive "no" until they had time to evaluate. Things that changed since Musk's original surprise announcement are 1) Twitter probably evaluated its future plans and worth, 2) Musk was forced to reveal concrete financing plans to prove it wasn't an offhand joke or a hostile takeover (recall, he bought a lot of shares in secret, which is an alarming sign), and 3) the stock market in general, and probably shareholders, reacted positively, which signals to the board the deal was worth doing.