Why redirect there?
It could be a strategy to make it harder to dispute ownership because it's not being used to Katherine's detriment, like hosting derogatory content about her or masquerading as her official site.
If the name was pointed at a page saying "name for sale" it might be possible to argue that the registration was vexatious. GDPR has meant that the registrant's contact details are no longer "public", it's not supposed to be possible to find out who the owner is. That does make me wonder how The Register has a trail of recent owners.
This is what Nominet say about domain expiry:
"Once you’ve gone over your expiry date, you’ll still have time to renew your domain before it gets cancelled, so there’s no need to panic. But if we don’t receive a renewal request within 30 days of the expiry date, we’ll suspend the domain name. This means all services that use that domain name, such as your website and email, will stop working. We’ll send you a suspension warning seven days before this happens, and will also send you a suspension notice when it takes place, unless your registrar has opted you out of receiving these. It’s still possible to renew your domain during this time.
When your domain has been suspended for 60 days without being renewed, we’ll schedule it for cancellation. We’ll send you one final reminder to renew your domain 83 days after the expiry date. As this is just seven days before your domain is scheduled for cancellation, you’ll have to act quickly if you wish to renew it at this last stage."
The way I read that, there's a 30 day period of grace then 60 days of suspension i.e. the address will not link to the web-site or email so it must have been unavailable but nobody (including katherine) noticed between 17 Sept and 17 Nov. (or did notice but didn't take appropriate action) so losing the name is no big deal, there are plenty of suitable variants.
If the friend's ex- was proving uncooperative during that 60 day period Nominet could probably transfer control even if the registrant name was "friends ex" (I needed to do something similar a couple of times and it worked).
In terms of traffic redirection, I guess search engines will have been getting an error for 60 days and either removed the name or allocated it much lower position in results so little value to the new owner - at least until there's news coverage like this so everyone goes to take a look...