Cracking paint

Hello All! I am painting my dining room chairs. I have already completed the hutch and table with no issues and it looks great! However, on the top of the back if my chairs (first coat) the paint is cracking. I am going to paint the second coat today in hopes that it covers it, but would appreciate any suggestions as to what I did wrong, need to do to fix it. I wonder if I didn’t get it cleaned good enough? If so, how do you fix that? I rewatched the painting chairs video and may need to use the wet stipple technique. Any suggestions?
Thank you.
*update: Added an additional picture after second coat. I still have another chair to finish that has the cracking, but so far only the one is showing after second coat. Still could use recommendations as I still have 2 more chairs I haven’t started painting yet.