Paul, they might be phishing around the site and may have possibly hacked some or all users passwords. Allowing them to easily hijack an account/s and use it to spam all over the site. If you're thinking that changing your password is pointless it's not. It could have taken them weeks or months to get it and so by changing it sets them back again and they'll most likely lose interest and hopefully move on. It's not a bad thing either to change it regularly which can help minimise the risk and the stronger your password is the longer it will take to be cracked.
You can test one here
https://www.betterbuys.com/estimatin...racking-times/