I think it shows a rather different story than what we've been lead to believe
No it doesn't. It shows one guy randomly following a couple of cops as he wanders through the Capitol building. Even if this was enough to exonerate this one guy (and it's not) it doesn't change the many hours of footage showing rioters violently attacking police, breaking windows, forcing doors, and committing acts of vandalism, etc.
There is not a single second in that video which shows a different story than what we've been led to believe by the rest of the video footage. Saying 'I saw one guy not doing anything violent in this brief snippet of video, therefore the entire narrative about a Capitol riot is false' is the same as saying 'I saw one BLM supporter standing peacefully at a protest, therefore there were no BLM riots and they didn't cause billions of dollars worth of damage.'
clearly the Police seemed rather more compliant and seemingly happy to show at least that one guy around.
No. They weren't showing him around, they were doing what other cops were doing: responding calmly to rioters who had entered but were not causing any trouble, while remaining close in case the situation changed. We already knew this from earlier footage. There are no grand revelations in this video.
What's the explanation there for those of us who haven't looked into it that much?
See above.
He did. When interviewed before his arrest, Angeli claimed he walked through an open door. But video footage showed him entering through a broken window. That lie did not go down well at his trial, where he ended up pleading guilty, throwing Trump under the bus, and offering to testify against him at his second impeachment trial.
not been given a guided tour
He wasn't, and this video doesn't show that.
'Senate Republicans condemn Tucker Carlson portrayal of Jan. 6. attack.'