When's the last time you ran on a treadmill? It doesn't do any work for you.
Not sure last time as I get outside to run, but used to do 10-15km a day a few years ago as it was too hot to run outside, and yes it most certainly does most of the work for you, it has a massive 5 hp motor, you are not propelling yourself through space, you are simply lifting your legs up as the motor moves the road under you rather than you using your legs to move yourself forward, hence running on a treadmill is pretty much effortless 15km on a treadmill is easy as while I could not do it out on the road where my limit usually is 5-7km.
The op is living proof of this, was doing massive distances on the tread mill, then did not even manage 2.4km in a real run, which I even at my age can do in my sleep.
Funny thing I used to see in Sydney is people fighting for the closest parking spot just outside the gym door only to go inside and walk on the tread mill, their logic always had me fucked,
Had a friend of the family who wanted to join the COPS years ago, he failed the swimming qualifications, as a result he joined a gym and started lifting weights, he never lifted before, so asked me for advice, I asked him why he all of a sudden started lifting and he explained that he failed his swimming and wanted to start training as there were more qualification swims coming up in a few months, I explained to him to start going to the pool and swim and that he was wasting his time going to the gym, he did not believe me suggesting he needed to be stronger to pass the swim, when I explained that he needed endurance not strength he lost interest in talking to me, three month later he again failed his swim
