Poor intelligibility of speech -speech therapy

[mama1nenene]

My dad is three in a few months. He went for a speech therapy assessment last week and I have just had the report back today. They say he has poor intelligibility of speech for his age and that the difficulty show signs of poor tone and strength of his oral musculature. He will be starting therapy sessions.
I am wondering what I did wrong, would things be different if I had taken to a speech therapist earlier? As a single mum I was unable to get off work to take him to the speech therapist when he was younger. I'm so confused and feel guilty that maybe it is all my fault. Will this be a problem for the rest of his life??

Guess I'm wondering are there other parents out there that have experienced this? If so can you give me any advise?? I feel like a failure, like I haven't given my son the skills he needs???