The Leaf's attitude toward Root was complicated.
Konoha had been established for more than forty years, and much had changed since its founding. Back then, it had been an alliance of small shinobi clans led by the two major clans, the Senju and the Uchiha. But as the Senju faded away and Madara Uchiha left, the clans' influence waned. After the Second Hokage's death and the Third Hokage's rise to power, the major clans' influence was weakened even further, and civilian shinobi began to rise in their place.
The major clans were still around, and they hadn't lost much of their strength. They held extremely important positions in Konoha, but the number of civilian shinobi kept growing, and their influence grew with it.
Was this something the major clans wanted to see? Could they tolerate it?
Of course not. Nobody wanted to see their influence diminish, and the clans weren't fools...
If they'd had nothing to gain, they would've rebelled long ago. But...
At some point, the clans began to realize that the wars were growing larger and larger, and more people were dying, yet their own losses were getting smaller and smaller...
That made no sense!
No, it made perfect sense. It was simple math: a huge number of civilian shinobi were being sent to the front lines as cannon fodder. A huge number of cannon fodder.
Shinobi from the clans were generally stronger than civilian shinobi, so they tended to serve in mid- to high-ranking roles. Their chances of surviving on the battlefield were far higher than those of civilian shinobi, and fewer and fewer of them were dying.
And so the civilian faction rose!
If you wanted others to die in your place, you had to give them something in return, right? Their share of the power