Outright ignorance is definitely pushing it. It's a guess, but very much an educated guess that it's mostly Brexiters who are googling it. Bremainers tend to be better informed, so they are less likely to be doing last minute (or in this case post-last minute) googling about the issue.
What a load of bollocks. The majority of people on both sides have been getting the bulk of their information from mainstream media, which is heavily biased towards a limited set of narratives. There's a fair amount of compelling information that has been omitted from or suppressed in the public debates.
In any case, we can't say for sure which side of the argument was searching for 'What is the EU?', though odds are it was a mixture of people from remain, leave, undecided and ineligible.