AITA for leaving a volunteer committee after it chose someone else as chair?

I handed over the storage-cupboard key at the end of the meeting and said I was stepping down.

Our seven-person committee organizes a neighborhood craft fair. I'd been on it for two years and put myself forward as chair. The members chose Olive, who joined last year. I congratulated her, then announced I wouldn't stay for another season.

People assumed I'd been planning to leave anyway. I let that impression stand. In fact, I'd intended to keep helping if I got the chair role. I felt overlooked, and the thought of reporting to someone newer made me resentful.

The fair is in three weeks. Before the chair decision, I had agreed to finish the stall map and collect the table signs. Olive asked whether I'd complete those two jobs before leaving. I said the unfinished map was in the shared folder and someone else could take it over.

She says I'm free to leave but not to make my existing promises vanish because the selection disappointed me. I said volunteers shouldn't have to stay where they feel unappreciated.

I haven't been asked to serve another year. I've been asked for the two tasks I offered to do this month. I can see that difference, but returning now feels like admitting the resignation was a sulk. AITA for leaving when I did?