It’s not a conspiracy; the City of London police, alongside normal local duties, have a national responsibility for many kinds of economic and cyber crime.
This almost certainly comes from long experience investigating fraud and other financial crimes amongst the businesses and people based there, to a degree and level of complexity not found in other regions of the UK.
For instance they host Action Fraud for the entire country.
If you want to talk about enforcement priorities, contact your PCC, or better yet, right now, your local candidates.
That's not at all the reputation they have. They've been acting as an extension of the copyright lobby for years:
• https://torrentfreak.com/new-uk-police-unit-announces-two-ar...
• https://www.vice.com/en/article/bvn4nw/cops-arrest-3-people-...
• https://www.cityoflondon.police.uk/news/city-of-london/news/...
There are probably hundreds of instances of them doing stuff like the above, that was just the results from a quick search.