My guess: Google's knowledge graph had references pointing to Joe Biden that, on inauguration, needed to be updated to Donald Trump so that answers to queries like "who is US head of state" don't linger on whoever happened to be president when they last scraped that information. In this process, they made the mistake here of replacing Biden's entry with Trump's entry, instead of appending Trump's entry.
> and what issues cause Google to continue it?
Seems as though it was fixed relatively quickly after it was noticed. May take a while for changes to propagate out, given Google's scale.
