It's not activism, it's the law in the UK.

The judge interprets how the law applies to the specific facts of this case. The law says extradition is not allowed in some circumstances. Those circumstances include how the prisoner is likely to be treated, and the health of the prisoner. Some other extraditions are ok according to the law because those factors vary in each case.

Not really. s91 of the Extradition Act requires that "the physical or mental condition of the person is such that it would be unjust or oppressive to extradite him", the judge must "order the person’s discharge".

https://www.legislation.gov.uk/ukpga/2003/41/section/91

There have been extraditions of other people charged with computer hacking offences like Lauri Love and Gary McKinnon where there was a similar concern. In both Love and McKinnon's cases, both were on the autistic spectrum.