Advice for quitting startup I founded

i'm leaving a startup i cofounded after 1 year because my cofounder and i have decided we're not compatible. he is the CEO, and it makes the most sense for me to be the one to step away. honestly, the last year was quite miserable with our dynamic so i'm pretty happy about it.

the question is: he doesn't want to tell our investors the real reason why i'm leaving (afraid of gossip, side picking), and he wants us to fabricate some other reason for why (he suggested saying i got burnt out, which i rejected as this is untrue and makes it look like i lack resilience, and i intend to start another company in the near future). what is the best narrative for leaving a startup you cofounded, especially if you plan to raise money for another startup in the future?