One might argue that the "Resistance" is not resisting sspx. Why? Because the putative leader, Bp Williamson himself, has written recently that sspx has done a good work, and is still doing it.
I have no less than 3 problems with your statements.
1. Bp. Williamson would be the FIRST to say that any of us could fall at any time. +W was fond of quoting Our Lord "God could raise up children to Abraham from these stones." He gave the warning that the SSPX could fall, years beforehand. The Resistance *has to* be larger than any man, even Bp. Williamson. What if he went Judas on us? Would that be the end of the Traditional Movement (or at least its sanest, non-Sedevacantist, branch)?
2. Related to #1, Bp. Williamson is not the Resistance itself, nor is he its spokesman. He is the oldest of the bishops, and probably the least active in terms of dealing with the Faithful i.e., the most retired of the 4 Resistance bishops.
3. You make the same mistake as many Pfeifferites, namely: mixing up one opinion, especially an exaggerated/simplified version of someone's opinion, and then taking it and pretending it's a dogma that +W is pushing "My way or the highway!". EVEN IF +W taught plainly and simply that the SSPX was doing great, he certainly isn't requiring *anyone* to hold to that personal opinion.
No one in the Resistance is required to place their right hand on the entire stack of "Eleison Comments" and promise before God to uphold and teach everything contained in these papers. But that is *precisely* what Pfeifferites and others act like.
In other words, that ONE POSSIBLE INTERPRETATION of a quote or writing(s) is far from a dogma that +W pushes on all and sundry.
Personally, I think it easily reconciles with reality/the truth, namely: the SSPX is still doing much good today, like a train that has lost 1/2 its workers and been mortally damaged. But a train doesn't stop on a dime. The train is doomed, yes. But it will be going forward on inertia for some time. Is there any evidence +W has gone beyond this true statement?
The same thing happened after Vatican II. This isn't rocket science. Any older Catholics should instantly know what I'm talking about. Why would an organization adopting Modernism result in 100% of its priests becoming Modernist overnight? Spoiler alert:
It wouldn't. As a matter of fact, those priests who want nothing to do with Modernism will have to die or be ejected before they'll ever be changed by the New Ways. They'll have to die out.