Jim Phelps in the 1996 Film Was An Imposter
A few years back after I watched the original M:I TV show for the first time I felt the same way that fans of it did regarding the twist in the first film, that there's no way whatsoever that's the same Jim Phelps from the show. Most people assume either that the films are a separate canon than the show (which isn't true at all, the special features on the DVD of the first film have dossiers of the characters which confirm that it's supposed to be the same Jim and same continuity), or theorize that the Jim Phelps we saw in the film was actually an imposter who impersonated the real Jim Phelps, who was either caught or killed prior to the events of the first film (perhaps during that recruiting assignment at the Drake Hotel in Chicago?). Well everyone, what I just discovered may shock you.
The other day I was trying to come up with ideas for another movie to explain and rectify this situation after all these years, that in this theoretical sequel it's discovered that a rogue former IMF operative with a long-held grudge against Jim Phelps sought revenge by impersonating him in the 1996 film to infiltrate the IMF, kill his team, and make Jim look like a traitor. Through my research not only did I discover that that's an entirely plausible explanation, but it actually quite literally already happened in the franchise before! This exact thing actually happened in the episode "Reprisal" of the 80s revival show! A former scientist/consultant with the IMF named Russell Acker literally impersonated Jim with a mask, voice, fingerprints, and everything and started killing Jim's former team members to frame him for the murders, as revenge for Jim putting him in prison. I don't want to spoil the episode any further so I'd recommend you go and watch for yourself, because it's entirely possible and even very likely that this dude could've been the imposter in the film!
Now if you're wondering how on earth this guy can impersonate Jim so well that people couldn't tell it was an imposter, the episode explains that this guy was a brilliant scientist who was actually responsible for advancing the masks and other IMF tech and spent literally 12 years planning his revenge and practicing his impersonation. Also the episode takes place in 1989, just 7 years prior to the first film so timeline-wise he could've easily broken out of prison 7 years later to try to get revenge again. Also ever wondered why the Jim Phelps from the movie was a bit more agile than his age would suggest? Well that's because Acker was only 40 in 1989 and would've been just 47 in 1996, which again lends credence to the imposter theory.
Now I know some of you may not care about redeeming the Jim Phelps character all these years later, but for those of us fans of the original show and/or the 80s revival (which I would recommend you go watch both) this is the best explanation there is. This isn't just some random fan-theory anymore, it's pretty much an iron-clad explanation that shockingly already happened before in the franchise so it's supported by very strong canonical evidence, and I'm surprised that to my knowledge it doesn't seem like anyone else has realized this before. My jaw was on the floor when I found this out, it's almost too perfect to just be a coincidence.