Don’t understand CIO method

Va

Hi moms. Struggling with my girls sleep lately (6 months) and although I don’t necessarily agree with it, I tried cry it out for her nap this morning. Looking for honest explanations, not looking to debate, but I’m not understanding how letting them cry when they’re this young is teaching them how to sleep. She gets soo upset and stressed out that she is wide awake and whimpering to a point where she can barely catch her breath (I let her cry for 25 mins and then I couldn’t leave her like that anymore) . I feel like if babies fall asleep after CIO, it’s from pure exhaustion, not because they’re realizing that’s what they’re supposed to do. I feel like it’s just teaching her that I won’t come. Before they can talk, babies can only communicate through cries. I don’t feel like it’s fair to her to ignore her trying to communicate with me, even if it’s just that she is unhappy in there... I don’t know - it could be that she banged her head while crying, something hurts, etc. I want her to understand that I’m there for her and she’s safe. I feel like leaving her to cry is creating a stressful association for her with her room and her crib which is the opposite of what I’d want. I know of the Ferber method, which is a better option for me but it still involves leaving her to cry and get stressed. Any advice is greatly appreciated!!!! Thank you in advance!!

PS - she’s teething for sure and maybe a growth spurt happening too. Not sure but I’m sure it plays into it