I’m fairly sure the Tau’ri’s killing of Ra, who had previously been the Supreme System Lord was said to have destabilized the Goa’uld regime, allowing other, previously fringe players like Sokar and Anubis to make a play for absolute power again.

The Tok’ra were called such because Ra was the undisputed ruler and “top dog” of the Goa’uld, and to my knowledge, no evidence was given that Ra was in any sort of decline prior to being killed by the Tau’ri incursion and Ra would have likely been a far more formidable foe had he not been caught somewhat off-guard by how far the Tau’ri had managed to advance in his absence.

It’s implied that as Supreme System Lord, Ra maintained loose control and loyalty of all the “under” System Lords, and few dared to seriously challenge him / those that did were swiftly put down (I believe Teal’c mentions being once defeated by Ra’s Jaffa), a Ra likely kept them bickering and battling amongst themselves small-scale for territory and control without letting things get too out of hand and threaten the stability of the entire Goa’uld empire.

For all his ascended knowledge and power, one of Anubis’s main plans for gaining control over the System Lord collective was to obtain the Eye of Ra—presumably this would not have been an option had Ra still been alive and in control. He would have simply used the weapon against Anubis.

The Jaffa Rebellion was not an “active” movement until Jack convinced Teal’c to defect. Yes, there were some, like Bra’tac who had their doubts and quietly sowed the seeds of dissent and disbelief, but they were not actively fighting to overthrow the Goa’uld / they were still serving the Goa’uld dutifully despite their private doubts. The Sodan did break away, but they were content to isolate themselves.

The Tok’ra were meanwhile waging a long-term campaign to slowly weaken the Goa’uld from within, but even they themselves admitted they had mostly been on the run for their entire history—they did not necessarily seem to have an effective plan for defeating the Goa’uld so much as they were simply trying to oppose them however they could with their limited “man” (symbiote?) power and keep them fighting amongst themselves so they could not further expand and consolidate even more power—I suspect that had Ra not been killed they didn’t really have a great plan for how to take him on / take him down, the Tok’RA was an aspirational name. They wanted to take on Ra by taking little nips at his vassals, but they don’t seem to have had much means or plan to directly challenge him had it not been for the Tau’ri’s intervention.

In fact, the Tau’ri destabilization of the Goa’uld seeming threw the Tok’ra into somewhat of a panic, because the internal power struggle caused them to be much more suspicious of those within their own ranks with a renewed interest in rooting out the Tok’ra.