Every year my mom was happy for her kids Mother's day gifts, but yelled at my dad for his gifts to her. Why?

I'm dreading this year's mother's day because I am wondering as a married 29F, why my mom should deserve a gift this year. Sure, she was good to my brother and I, but why did she treat my hardworking dad like crap? Every day. She was so loving to us when we gave her silly gifts like a fruit parfait and a homemade art card but when my dad buys her roses, her favorite flower orchid, and her favorite chocolates and balloons, and takes her out on a lunch date, and airpods, she rolls her eyes and screams at him!

So ungrateful. My dad don't have that much money, he's paying all the bills and full time Coast guard job, and has no time to rest, and yet she told him to return the expensive gift. So he goes to Apple on that same day to return it. And then she complains why she keeps getting "cheap" gifts on Christmas?! Wtf?!?!

And dad told me two years ago that he only stayed in this relationship "because of the kids" is that supposed to make me feel better? Wow what a good father for sacrificing his mental health, wearing a happy mask every day and enduring the emotional and physical abuse it makes me so sad... She never directed the abuse to her children, but as the oldest child I felt traumatized, too. And now, I feel like a bad guy for planning to not text my mom "Happy Mother's Day <3 I love you!" because of the way she treated my dad in the past.

Would it be ok to slowly go no contact? Why do I feel like a bad guy?