Here’s what happened:
You were overweight, decided to lose weight rapidly (about 2lbs a week), and still don’t quite look like you lift. Because you don’t have experience in building muscle, you didn’t have the experience to retain muscle during a cut. I think your cut may have been too aggressive and wasn’t a good decision.
I’m 190 and 2600 calories is a big deficit even for me - and you were 70lbs heavier and are currently 40lbs heavier than me. It’s also counter intuitive to eat double my maintenance calories (3000) to put on size.
I’m pretty certain you didn’t hit 260ish off eating clean. I think your diet now is good, but I just scale it down. Find your maintenance calories if you need to work off a number and go with that.
As the video states: eat single ingredient foods, eat when you’re hungry, and eat till you’re full, and be active.
I should also state that starting strength is not going to be the best plan for you at this time. To me, it’s just not enough volume to build muscle. I’ll always recommend 5/3/1 Boring But Big: