a few million people WISH they could do things like this but it costs money to survive

I don't think money is the only issue. You're also having to take so much time away from family and friends. I think many people would rather have a pretty normal life instead of dedicating years and years to a massive expedition. Hats off to the guy though, it's quite an achievement.

From the wikipedia article:

From late 2008 to 2010, Bushby spent his time in Mexico for cost reasons and was unable to travel to Russia. This was both because of trouble getting a visa and permits, and because of financial trouble; Bushby lost several of his sponsors due to the 2008 financial crisis. After Bushby secured new sponsors in 2010, the Russian government issued him another visa, and he resumed walking across Russia in the spring of 2011.

So basically he takes breaks, keeps the costs low and has sponsors, but financial troubles are absolutely an issue.

Read the wiki article above, it has links to other articles where it's sourcing its information.
Link to article documenting his expedition across the frozen Bering Strait.

"Karl Bushby reached land after 14 days walking across shifting plates of ice in temperatures reaching -30C." "The ice was breaking up behind him as he walked across."

However, it does appear that some of his walking has been replaced by swimming.
"In August 2024, Bushby started the swim across the Caspian Sea from Kazakhstan, planning to finish in Azerbaijan to avoid going through Iran or Russia, as both countries were then too dangerous to enter with a British passport. Bushby was accompanied by co-swimmer Angela Maxwell and two Azerbaijani national swimmers, Anastasiya Boborikna and Abdurrahman Rustamov.[15] Each day, Bushby and company swam in two 3-hour sessions: one in the morning, one in the afternoon and resting and sleeping on support boats each night.[16] The swim covering 179 miles (288 km) was achieved in 31 days with 132 swimming hours.[17][18] From Azerbaijan, Bushby then went to Turkey to cross the Bosphorus Strait into Europe"

~~He'll probably end up swimming across the English channel.~~

Regarding his trek across the English Channel:

Karl relates in his book that he hopes to walk through one of the service tunnels of the Channel Tunnel Tommfuller (talk) 12:03, 7 January 2009 (UTC)

TIL Scotland and Wales don't exist

Most jobs are a pointless waste of time that are upheld under the threat of starvation and destitution, and I say that as someone fully employed.

the real shitpost are the friends we made along the way

It's also an incredibly stupid bureaucratic clusterfuck of the magnitude that only customs and border people can achieve. Surely there should be some mechanism wherein you can send a letter or something to the Russian authorities to inform them, "Hey, we're trying this stupid stunt and here is our plan, let us make our declarations now and we'll pick up all the paperwork on the way once we get there." But there probably isn't, and then you wind up with crap like this.

The tinniest of tin-pot jumped up little dictators are never to actually be found in your nation's capital. Instead they're all lined up along its borders acting like these various lines in the sand were laser-etched there by god and aren't ultimately just arbitrary and, indeed, historically much more fluid than they'd like to pretend.

Pipi post?

Imagine you have a hobby. You get really good at it, and somehow, the hobby pays for itself. You get to quit work and just do your hobby every day.

Imagine your hobby is hiking.

I mean... Isn't that how humanity rolls? Historically speaking anyways, 99 out of 100 people live and die close to where they were born, while the oddball goes and does a Leif Erikson for his whole life and then we get Iceland. His psychology compels him to do this.