The reason for the protest does seem a bit niche - presumably next week there'll be a splinter group of the splinter group of Extinction Rebellion called "Double Glaze Britain", followed by a splinter group of the splinter group of the splinter group called "Please shut your front doors Britain because you're letting the heat out - were you born in a barn".
Given the thousands and thousands of people held-up, it is more likely than not that people will have missed flights, important appointments and medical treatment; being late for work may 'just' be an inconvenience, but for many the delay would have been much more important.
I too struggle to understand why the police didn't simply drag them away as soon as they arrived on the scene.
The protesters are pathetic bedwetters who deserve all of the vitriol flung their way - they certainly don't appear to have won a lot of support.