Which isn't really all that special. In England alone, there are 816 churches named after St Michael. He's pretty popular. It'd be a lot more spectacular if they were all named after someone much more obscure.

https://en.wikipedia.org/wiki/Dedications_in_the_Church_of_E...

Only ~30 are cathedrals, still more than a selection of 7.

https://en.wikipedia.org/wiki/Cathedral_of_Saint_Michael

Right, but none of the 7 are cathedrals.

That's right. I would actually expect there to be a few more than 7!

And if we extend the search to all placenames dedicated to St Michael quite a bit more!

It's not pure coincidence but it is a kind of observation error as highlighted in other comment. Increasing and decreasing the variables and measurements effects the odds.

Basically you can get a line between many things on earth, but 1) the dimensions of that line cannot be chosen if you also want to choose the things that define it or 2) the dimensions can be chosen but the things that make it up cannot.

In that case he should plot which of them match the geodesic line curve

If one finds all of those lines one might find something.

Also compare star maps.