[tankenmate]

Actually the recommended data handling says you should specifically state the purpose for needing the data, and that it should be reasonably limited to that need; i.e. if you don't need it any more you should pro-actively delete it.[0]

[0]https://ico.org.uk/media/for-organisations/documents/1475/de... Pages 4-6

[drchaos]

They do have a legitimate interest (in the sense of article 6(1) of the GDPR), namely providing an internet archive.

[tankenmate]

I would agree in the case of the wayback machine they have a very strong case under article 6(1).