It was bitcoin guys doing it as a mild troll but mostly to bring attention to people about bitcoin. Central banks have been screwing us for a very long time. The fractional reserve system is a total scam, a literal ponzi scheme & it’s starting to unravel.
It all started with just a harmless troll to gain attention from the people about bitcoin but it is already safe to say that the authorities are now tracking down who's behind this movement to make an example because the place where they've flashed the logo wasn't a random building nor a coincidence, it was the European Central Bank and I bet it was planned.
Hopefully many people see the logo & decide to look further into bitcoin & what it can do for them.
I got no doubts that many people have actually saw it and in the aftermath, many people will know it as that will surely make a headline for days.