I'd be interested to hear about the last time a team took a clear lead in the title race in August and steadily maintained it through to May. And I'd be even more interested to hear about the time before that.
It is extremely rare. One of the reasons is of course that every team, bar none, goes through a bad patch at some point. Injuries at the wrong time, suspensions, off days, fixture congestion.
Also, Big leads have strange effects sometimes. It can do strange things. An 8 point lead becomes 5 points, with the title rivals to play. Nerves can creep in, the crowd gets anxious. Within a few weeks a big lead can become a slender lead, or even no lead at all.
It is never good to be off the pace but anyone who genuinely thinks the race is over (rather than saying it in frustration and anger, like most have done) is seriously misguided.