They can tie it to you by cross-referencing all the signals they have about you with data collected from other data collectors and aggregators. With enough data they can connect things like browser fingerprints and so-called anonymous ad IDs with your real identity.
Keep in mind that there is a good number of technical people whose job it is everyday to continuously figure out new ways to track everything they can about every person they can. These data collector and brokers have demonstrated time and again that they don't really care about following the rules either. Here's a good resource for more info https://noyb.eu/en
In terms of how they use it against you, this is some good info and it applies even if you aren't American https://epic.org/issues/consumer-privacy/data-brokers/