Technically they could, but once fiduciary duty is considered, and also given recent drops and maybe less than spectacular q1 results which as I understand are to come soon, they probably decided they shouldn't, as this may expose them to torches and pitchforks from shareholders that are less ideologically driven than they are.

Yes, Musk's bid may be overpaying, but in that case board's duty is to grab the money - and that's probably why he is overpaying.