There's rarely any original player left, which should be obvious by now.
As people get bored, they're replaced with new owners. The accounts with original owners are often leaders or players who's just as stubborn and I hardly believe that anyone of us see this game as fun. I don't know if Sciros got issues with getting owners, but we constantly replace players in TSE as whenever we need. At some period a few players will be more inactive than others, but in turn we'll also have active players to cover for them.
If a tribe constantly lose villages then it wont help with re-nobling elsewhere, since the map wont expand further. This means that as we break fronts, then the enemy will keep having a harder time which will need more activity. If the player gets overwhelmed and sick of the game, then that player will likely go inactive or quit later on. It's rare that noble whole players in one sweep, but if we take most of their villages then they'll question why they play. If you never had a plan, then it might be hard to understand. Every experienced player should know how to win a server, the question is who's up for the task and who will be able to accomplish it.
You're likely a new owner and have joined from a new world. In W5, our fronts are what they're, there isn't tribes left to right everywhere on the map. So when a tribe falls, then it falls.
Even if players left after a tribe being dissolved, they'll not make it on their own. A tribe works together, and when it do, then taking out skilled players is not always an issue. Skilled players taking out an entire tribe is however an issue where the players run out of nobles.
I hope that it doesn't come as a chock, that many of us play to win and not for fun.