ok u know how ryan and spencer are like ultimate bffls and probably had those necklaces that are like...half a heart that says best and the other says friends? like they were RyanAndSpencer and when they started the band it became RyanandSpencer and Brent but Brent was like...never fully there, you know? it never really became RyanandSpencerandBrent and brent was always kind of separate and then Brent brought Brendon to practice and one can assume that possibly Brent thought that either a) Brendon would bridge the gap between RyanandSpencer and Brent, or b) Brent wouldn’t be quite as far on the outside (RyanandSpencer and BrentandBrendon-type scenario) but in reality Brendon was able to fit in pretty well with RyanandSpencer and two things happened: 1. It became RyanandSpencerandBrendon and Brent and 2. BrendonandRyan happened. During the recording of Fever (when Brent apparently was not around to record his parts and such) they were staying in a one bedroom apartment in Maryland, and if Brent was feelin super isolated it would have been hard for him to get away from it, especially considering i think Ryden might have weirded him out a bit (not in a homophobic way, just in a ‘This is weird you are my friends I am uncomfortable” way), whereas i think Spencer would’ve been kinda stoked about it? idk i get the vibe that he would take it completely in stride and just be like “yeah dude ok my best friend is fucking our new lead singer who is my other best friend this is chill this is rad” but in Maryland Brent would have been able to leave the apartment and hang out with other people and kind of get away from it a bit? but on the Ambitious Ones and Smoking Guns Tour (when they supported The Academy Is... from January to May, also hello Jon Walker) it would have been significantly harder for him to distance himself from the group dynamic (RyanandSpencer, RyanandBrendon, RyanandBrendonandSpencer that he didn’t really click into, hence him being MIA for periods of time and eventually not showing up to the Weenie Roast, where Jon played with the band for the first time
tl;dr i think Brent was a) weirded out by Ryden, b) felt kind of isolated from the group, and c) i don’t really think he ever expected the band to take off in the first place