With satellite trackers and social media these kinds of events have developed into a spectator sport. Bikepacking races tend to be in more remote locales than the French countryside so racers are required to carry a satellite tracker which reports to a public website. "Dot watchers" who live along the route come out to watch racers go by or leave water/snacks in coolers along the side of the road. Far more dot watchers are limited to the live tracker and check daily updates from racers or journalists covering the event on social media.
After the event some racers upload videos for spectators and it helps them with sponsorship. This video gives a glimpse into what its like to race the Tour Divide competitively. https://www.youtube.com/watch?v=azJS106xeNA
What I mean by a "spectator sport" in this context is primarily that the event can be monetized because huge numbers of people will watch it either in person or via video of some sort.
The number of people watching the trans-europe or other similar solo events as they happen is likely less than the population of a typical US liberal arts school. The monetization that might follow from YT videos that occurs later is completely different from what the TdF manages to encourage. The winner of 2023's Tour Divide has 58k views ... even Lael only gets 300k or so views for her adventuring and racing videos. This is not a spectator sport in any sort of historical sense of that term.