Scott takes off, because, of course—almost as quickly established as it’s introduced—he doesn’t really die fighting Matthew at the end of the first episode. It’s eventually revealed to the audience, and through Ramona’s own investigation over the course of the season, that Scott has been kidnapped… by none other than his future self (played by Will Forte in a delightful turn), one who wooed Ramona, defeated all her exes, and then dated her before growing apart, and becoming distant and bitter in the process.
So his plan is pretty much to kidnap his past self, show him what a terrible person he is, and then blame it on Ramona to try and twist young Scott into never dating her in the first place. Which would be interesting, but then Takes Off layers in a twist that Future Scott laces his past self with nanomachines that prevent him from being able to kiss Ramona, setting up a big battle between everyone and a hulked-out Future Scott at the end that is very visually fun but… just kind of a weird sideways jaunt.
The whole point of Future Scott growing apart from Future Ramona was his own communication issues and unwillingness to actually talk to people, so the fact that Takes Off almost has to end with a big scrap instead of navigating that in a more nuanced way is a little disappointing.