That is a very good question. Bet someone with juice had a cow about traffic and/or parking. If so, there's probably a comms trail that's being shredded and/or deleted as we type. Or the contractor/s could've promised that this was no biggie and traffic could roll. Hopefully an honest and thorough investigation will sort it all out.
Security camera footage of walkway collapsing, as reported and shown on Miami Herald web story:
https://twitter.com/OfficialJoelF/status/974477515594059776