Something like 97% of the CCTV cameras in the UK are private, just like the one in the article.
The issue is he set it up without complying with GDPR rules. If you set up a CCTV system that can record public areas or land you don't own, the data collected needs to be reasonable and you need to notify people you're doing it so they can request to have images of them deleted. Any organisation running CCTV in a public area will likely have performed a DPIA, including police, local government etc.
Our right to privacy is a bit stricter than the USA. You don't have a right to privacy as such regarding photos taken from normally accessible public areas. If you're out taking photos in public then you won't have anything to worry about from a data protection perspective. However, if you're recording 24/7 or commercialising that data, you have to be more careful. If you're doing things like going up to people's windows and taking photos into their room or flying a camera drone at low altitudes over their private garden, you might also have problems. At the very least you should do a DPIA.
Also this fine may be overturned on appeal.
Side note: if you measure like for like, the USA probably has more CCTV installations per capita than the UK.