Yep, a lot of people saw this coming. It was so obvious - new powers are always abused in the end. Same for the UK. Perhaps the politicians knew that and didn’t care. Not sure how deep their cynicism / malice goes. More power to us, they said.
The UK however had pre-existing authoritarianism due to the Troubles. Acceding to ECHR in Northern Ireland and rolling back the authoritarianism there in favor of an external human rights court was a critical part of ending the cycle of violence there.
In the UK there is a big element of sheer incompetence. Politicians who have not experience of life outside politics are really will-equipped to understand the consequences of what they do, and defer overly to expert opinion. Of course the police or intelligence services say they need more powers, it takes judgement to balance this against other considerations.