What felt like 5 feet was probably a vibration of a couple inches.
Maybe the architect had one of those DEI degrees
Still, a couple inches on something that high is a lot of compression and spring back for a steel and concrete structure, unless the structure is purposely engineered to flex.
Something that huge weighs plenty, which means foundation peers going to bedrock. If the foundation shifted an inch or so, that would do it. Unless the building has major structural issues, then a collapse in imminent.