As Carl points out this was originally just sailing, running and walking with no motorized transport at all. The modern version of that now uses Whitehaven rather than Ravensglass to access Scaw Fell Pike and so allows cycles for the first 15miles from port.
As for the car version - there are around 35,000 people do this every year, most do it within a few weeks either side of mid-summer and mostly weekends. This is putting a huge stress on the environment over that period. The Scaw Fell bit is done in the middle of the night with lots of vehicle traffic on very narrow country roads. The National Park are having to collect a huge amount of litter from the area as people are discarding used drink cartons and food wrappers. Even when its put in the bin, they're having to empty bins every day that usually only get emptied once a week. As what goes in must come out there's also a lot of rather smelly waste from the other end of the body that is causing such problems they're having to provide Portaloos this year.
A large chunk of this challenge is taken up with driving, with the impact that has on the environment, but it also gives the challengers a fair bit of rest, its getting away from the concept of a challenge that you should be challengeing yourself and being self-reliant.
There are other challenges that are more challenging to do, more pleasurable to do and do less harm to the environment. There's the coast to coast walk or cycle, the Pennine Way, Hadrian's Wall. You could do a number of Wainwrights, a number of Munroes, The Bob Graham Challenge (41 Lake District Peaks), I have a mad idea to do all the 800+m ones in the lakes once an injury has healed. There's loads of existing challenges and no reason not to make up your own.