This is something I think about a lot, and I've been meaning to make a post about it for a while
One of the things I love about Crystal Skull and Nick as a character is the retroactive effect that has on Daniel's entire storyline
Not only him being abandoned yet again, but also "I'm not crazy"
That's practically his mantra throughout the first couple of seasons, every time anything happens that someone else doesn't believe him about it's like the first thing he jumps to
The retcon of Nick existing and his whole story makes it so that Daniel is not just still fighting against his memories of those other professors from long ago, it makes it seem (at least to me) more like he's terrified of inheriting whatever "craziness" Nick was diagnosed with (was it schizophrenia or something else? I don't remember)
When he had his theory about alien landing pads and people called him crazy, it was certainly an echo of his grandfather's own fall from grace with one key aspect missing: the "hallucinatory" experience
That doesn't come until There But For the Grace of God, when he's had this experience of traveling to an alternate reality, and he KNOWS it was real, but his friends don't believe him and it's implied he keeps telling them the story over and over again to convince them it's true, and in those last few episodes of season 1 he says "I'm not crazy" quite a bit
There are other episodes where this comes up but I'll skip to the biggest one, which is of course Legacy
If we ever needed proof that Daniel lives in utter fear of one day turning into Nick, this episode is it
The way he says "I'm having some sort of nervous breakdown," the way he's so determined to insist that he's fine and it's not a big deal, "I'm not crazy, I'm not crazy," I'm not my grandfather, I'm not my grandfather
He's so miserable and scared the second he gets committed, and he's so quick to accept the diagnosis of schizophrenia because he thinks "Oh God it's finally happened, I have become Nick, I did inherit his mental illness"
(Side note: Jack is really really good at dealing with Daniel's delusions in this episode, he advocates to make sure Daniel isn't being medicated against his will, he knows to ask if Daniel is being mistreated in the mental hospital, the way he says, "nothing worse than losing your mind and knowing it's happening," it seems to me like Jack has watched someone he knew and cared about go through this kind of thing before)
Anyway this has all probably been said before but I think about it alllllll the time and just wanted to get it out there