I've only recently become interested in the Lucy Letby saga. I have to say .. while claiming a belief in innocence might be a step too far (for me, at the moment). I would hesitate to say it is anywhere near obvious that she is guilty.
This case doesn't have any solid evidence to it at all and was entirely built on the presumption of suspicion, rather than an investigation where all possibilities were treated equally. The death of each baby has not been analysed as 'these are the findings of death – what happened on the ward that day and prior?', they have been treated as 'if Lucy Letby was responsible, how might we show that?'
Police just want a conviction. They don't care if the right person is convicted. And that's tale as old as time.