Don't forget that Smash even made a big deal of Charizard, giving him a trailer along with Greninja. Nevermind that Charizard was already in Brawl, and that its moveset didn't change much between games.
Can't blame them, considering there were nods and appearances of Charizard in the last four gens without the other two, with Gen VI and Gen VIII rubbing more salt in the wound, first by giving Charizard two forms, and then
I think Sceptile didn't make it because they wanted to add someone that represented the then-new FireRed and LeafGreen instead of RSE (in fact, I don't even think they even considered it), while Ivysaur made it so that Pokémon Trainer could have a medium character, a big character and a small...
At least in my case, it was due to that special forme. I have always felt that for all the complains about Charizard shilling, this was one of the times where it could have been appropriate. Sadly, they had to create a then-anime-exclusive forme just so that he could compete with Megas.
Well, that was because Munchlax was among the first Gen IV Pokémon revealed. Once Gen IV got released the poor thing got dropped from the face of the Earth almost immediately. Same thing happened to Zorua when Gen V came.
Yes, but I think that was due to lack of communication between the Western and Japanese fandoms. Not a lot of people here knew about GS, unlike the Japanese fans that knew that Gen II was coming since the month the anime started airing.