How? As far as I know a commercial company can't get your location or other personal information just by knowing your mobile phone number?

You are fooling yourself here. They probably have a whole data cake already, they want the mobile number as a cherry topping on this cake.

You know about the anonymized and aggregated data that one can buy ? Well it can be easily anonymized and deaggregated.

The good part is that you don't even have to do it yourself and go directly to data brokers that have done the hard work for you.

Coming from the standpoint of a very curious independent researcher, I'm curious what I might query/search for to learn more about these data brokers.

Not at all out of anything that might be categorized as malice, just to add this datapoint to my mental map.

Buying data lists. You usee your mobile number to get your cinema ticket - or whatever - the cinema sells that data. Do you get package alerts when you have a parcel due, now your phone number is joined to that address, plus presumably the credit card companies sell their data (?).

Companies amalgamate that data, then sell lookups of varying degrees.

Screwfix in the UK gather a lot of personal data as part of their sales process, they're the least covert about data gathering I've seen.