He came back from being stale. His times were slowing. He had less zing at the end of races. That improved after the three successive 22 milers. That's pretty much been established early in the thread.
Long running, done correctly, is going to strengthen you. Lydiard's long runs were always done at manageable paces and by people who had done enough mileage that they were able to benefit from long runs. Guys like Magee and Puckett had years of 100 plus mile weeks behind them. If you have a typical US collegiate runner who is maybe doing 50-70 mpw do three 22 mile runs in a row you may well kill him because he hasn't got the background to manage successive runs of that length. If you toss in the fact that he thinks he's a stud who should never, ever be caught dead going slower than, say 6:30 pace, the problem gets worse.
Even if you do the runs correctly and have the background to benefit from them you will feel pretty wiped out while you do them. But once that passes you'll be much stronger. In 1958 Lydiard came out of "retirement" to help Ray Puckett get into the New Zealand team in the marathon for the British Empire Games in Cardiff.
At one time they ran the Waitairua 22 mile course four nights in a row. As they set off on the fourth night Puckett said, "My legs are raw." Lydiard answered, "Mine are too." And off they went. Puckett made the team later on. Being fatigued is normal for people running big miles.
But even when the fatigue passes normal Arthur still believed in using long runs as a restorative. One of his later quotes was, "If you become over trained, do a 20 mile run at a pace so slow that grandmothers pushing baby carriages are passing you."