I see a pattern here.
Yes, the Resistance is a legitimate movement. But no one can stop an unscrupulous, bad, vice-ridden, shady, or similar priest from attaching himself to the movement for personal gain.
It's not as though there's a central authority which issues "licenses" to any priest claiming to be Resistance. No, it doesn't work that way. The faithful are desperate, and even if, say, Bishop Williamson had a "red list" of priests to avoid, many Faithful would ignore that warning and seek out those priests anyhow, because THEY ARE DESPERATE.
After all, it's the wild west right now. Everything is in flux, everything is in the germ or seed stage. There is extremely high demand almost no supply.
Just like the Trad world in the 1970's. Just read your Trad history books about what various independent Traditional groups went through in the 70's: lack of priests, fake priests, bad priests, weird priests, Bishop Shuckardt, you name it.
Long story short: the Resistance is basically another beginning for Tradition. Beginnings mean privations, change and lots of OPPORTUNITY. Where there is opportunity, there will be opportunists taking advantage of the situation to enrich themselves. That is how life works.
Priests who wanted more travel will get their travel. Priests who wanted more good food will get their food. Priests who wanted to live in a different part of the country can now move there. Priests who chafed under obedience need not obey any longer.
There are plenty of Faithful desperate for a priest.
Some priests will join the Resistance for noble motives. But unfortunately, for every living Saint who does this, there is another who does it for mixed, or even bad, motives.
Consider refugees from a tyrannical dictatorship: many good people will leave for good reasons. But many criminals with nothing to lose and everything to gain, trying to evade the authorities, will happily blend in with the refugees as well, looking forward to a new start in another country.
The Faithful must be careful.
Any crisis brings out the worst in some, the best in others.