Why did my beloved dog have to die?

I have had a horrible couple of days. My favorite dog, unexpectedly passed away. I was the one who found her. I tried CPR & trying to hit her mouth with some water to attempt to just shock life back into her, but I was just a few minutes too late. I’m absolutely devastated. I sat outside with her because I was too scared to move her with how heavy she was. I stayed for the next 40 minutes til my husband got home & picked me up first & then picked her up. All I could do was tell her I loved her & im so sorry. We don’t know what happened. She was only 2.5 years old. She began having some issues back in February, but she had been to the vet & the vet had been monitoring it all & at no point did ANY of us expect this. We are assuming it’s related & she must of had further issues internally we just didn’t discover. With how quickly it happened, I feel confident it had to be a heart attack maybe or something that caused her to just lay down & that was it. She wasn’t outside just left or neglected. She was outside for her bathroom break & because it was so beautiful & all the dogs were all playing together, they got extra time to just hang out. She was playing & her happy self. I JUST took a video of her & then went to switch laundry & lay my son down for his nap & as I came back to let everyone inside, I already knew something wasn’t right bc she didn’t budge when she heard me & she will snap out of the deepest sleep when she hears your voice. The whole thing was soul crushing. It was traumatizing. I can’t stop replaying the entire day & the situation in my head. I just wanna cry. I missed work yesterday bc I couldn’t deal with it & now I have to go in today & I just am not looking forward to this. My sweet girl. Why did it have to be her? 🥺😩💔

Thank you if you stayed with me & read this far. I know it was a lot.. but it feels good to let it out bc I just haven’t.