I can get it based on braindead executive logic, but on every other level, it is so baffling that they keep throwing money at this whole Spider-Man Minus Spider-Man idea.
Like, they're doing it because Venom actually worked, when on paper THAT seemed like it'd be a terrible idea. But like, we can look at that with a wider lens now:
Venom was a bad idea because... we're seriously making a movie about Spider-Man's evil costume that doesn't have Spider-Man in it?
Even having seen the results that's a hard point to argue, BUT, back when he was first introduced, Venom actually was this huge breakout character that people wanted to see doing stuff independently. People wrote a lot of Venom-focused stories, did a lot of work on how this character works without Spider-Man being there, developed this whole '90s-comic-antihero thing. And even though they didn't actually use it, hey, you already introduced him in a movie.
Venom was a bad idea because the last time they tried to put Venom in a movie it kinda killed the franchise and they had to do a terrible reboot nobody liked.
Yeah, executives forced Sam Raimi to cram Venom into his third Spider-Man movie because again, popular character, and he really didn't want to, and kinda did so under protest, and then kinda went screw the whole thing. The actual lesson to learn there is that when you have a director with a strong personal thing making you a ton of money, just let them continue to do their thing and have a good time, that'll probably work out, and if you try and reign'em in too hard you'll strangle the goose laying those golden eggs.
Venom was a bad idea because Venom is a lame edgy '90s anti-hero and people are so very over that.
Turns out if you're aware of that and lean into it the right way it can work out. Especially since they decided to pair that up with making it a very '90s-superhero-movie sort of thing, where there's that short running time and weightlessness to violence to offset the whole deal, and hey, people are also really burnt out on over-serious overlong movies so that works out as this refreshing breath of fresh air/nostalgic thing. And they just had a lot of fun with the character, lucked into an actor with a quirky take and had a surprisingly great supporting cast and particularly in the sequel leaned into the queer stuff, so yeah, that came together.
But like, that first obvious problem is still a really huge one here. There really aren't any other big breakout Spider-Man characters who can carry a story on their own. Or really if we're honest, any interesting characters at all. Like everyone likes J. Jonah Jameson, particularly as played by J.K. Simmons, but he simply cannot exist in a world where there is no Spider-Man to demand pictures of. And people like/have even heard of Dr. Octopus. You could probably make a Dr. Octopus movie work under the right conditions. But past THAT? There really is just nothing to work with here. Maybe some characters who are clones or alternate versions of Spider-Man, but those are gonna be off the table. Everything else in the IP box only works when bouncing off Spider-Man, if they work at all (and honestly that's a big if, there's a reason adaptations of Spider-Man frequently just come up with their own villains and stuff that wants Spider-Man to have friends and allies ends up crossing over with other comics all the time).