Stab in the dark but I imagine some of those campaign website domains lapsed, were picked up by domain expiry people because they probably have very good visibi

Stab in the dark but I imagine some of those campaign website domains lapsed, were picked up by domain expiry people because they probably have very good visibility (i.e. a lot of links to those pages from official/.gov sites), and had phishing or sketchy landing pages put on them. Google then prunes these malicious pages from their search and then also flags any docs that have those links in them.