All good points, but I think your conclusion is still wrong. The fishing expeditions are indeed a strategic objective, but not the lone one. Satisfying the base's sense of butthurt and revenge over Trump's impeachments is still at least equally important to the GOP.
I think it's also helpful to remember that both of these objectives are fundamentally driven by their side's chaotic propaganda complex. There isn't some central plan which was hatched in McConnell's turtle lair years ago and is only now coming to fruition. These guys are riding the tiger. The most coherent plan they can manage is whatever McCarthy whips up in his office on any given day to placate MTG's Twitting and Truthing.
My point is, we have to stop thinking of this as a deliberate plot, but instead more like a house party where the entire football team showed up and doesn't want to leave because they're too hopped up on uppers and aren't going anywhere for hours, if not days.
So, the fishing expedition will do its best to unearth whatever innuendo or trivially petty nepotism it can. But at the end of the day, they aren't doing it because they believe there are or aren't any fish in the pond; they're doing it because whether they plan to or not, they're going to drink a lot of beer and make up some utterly fucking ridiculous fish stories even if they never see a single fish.
Likewise, they're going to impeach Biden -- or at least go through the motions of drawing up articles, having some sort of hearings, and threatening to if not holding an actual vote -- not because they ever set out to impeach him or not, but because drawing up articles is a hot January new-session fundraising-blitz email for MTG to send out, and having hearings is just another chance to serve up a new tray of Kool-Aid on Fox News and Truth Social and wherever else.
IMO, the difference is that a plot is something that can theoretically be foiled. Most Dems seem to hope that if you just intercept McCarthy at some key stage in his "plan", you'll be able to short-circuit the fishing expeditions or the impeachment. But you won't, because there IS no key stage in the plan, because there is no _plan_.
Whereas, the out-of-control house party requires entirely different methods to wrangle. Call the cops. Drain the keg and take away the drugs. Announce that the hated rival team's players are keying everyone's cars. It's not a plan to foil, it's a situation to contain.