Bergoglio has admitted that the Motu groups have served as a "gateway drug" or "halfway house" to Catholic Traditionalism. When the faithful get exposed to the True Catholic Mass, it tends to make their doctrine orthodox as well.
Yes, I think the inherent graces of the True Rite (even if an indult) were underestimated by the Modernists. +Benedict crafted the motu latin mass to capture the lukewarm Trads in order to weaken the sspx/Traditionalism. And, based on my experience, this worked marvelously. A high % of Trads (most in their 20s-30s), left True Traditionalism for the indult/novus ordo.
What the Modernists didn't count on was the high conversion-rate of protestants/novus ordo-ites who had never been exposed to the Latin Mass and its graces. And also the indult communities (St Peter, ICK) also started downplaying the novus ordo and started speaking out against V2). The gain of Trads to Tradition very much outweighs the loss of many young Trads to the novus ordo.
That's why +Francis has to "stop the bleeding" of young people leaving the new mass. One small crack in the V2/new mass dam, and the whole thing is beginning to crumble. +Francis can "crack down" all he wants but I think it's too late. Traditionalism will return in glory, very quickly, once we get a holy pope.