I think it's most likely no coincidence. Sometimes online shops - especially those offering particularly good deals - have this as the downside. Have a look at the privacy agreement, or purchase agreement that should have been part of the transaction. If your address has been sold to other companies, the details of what they will do with your personal information should be in the agreement.
Or it might be less sinister....a "service" provided by the original vendor to keep you up to date on the latest specials.(Seems fairly likely to me.) If this latter is the case, often there is an option to "opt out" of these offers.