I believe it was Trump and Elon Musk falling out over the "Big Beautiful Bill". A lot of people then campaigned for to get the job anyway, and he did.

After Artemis II, there was a moderately hilarious congressional hearing in which the Republicans insisted on giving NASA more money, the Democrats insisted on giving even more money than that, and Isaacman trying to say "we're good".

(I believe NASA got the more money.)