I think, like Sununu, Baker has his eyes on a bigger prize. He’d lose against Warren in a presidential year in Mass (and if he didn’t, y’all can go fuck your so-called liberal selves). He seems like more of an executive type, less legislative, but I can’t claim to know him that well.
Seems to have accomplished a lot for Massachusetts, which, barring a GOP trifecta in Washington come 2024 (not entirely out of the realm of possibility), he wouldn’t do in the Senate, outside of tax cuts.
I really don't know what Baker wants now. I agree that he sees himself (and is) more of an executive than a legislator and even if he won the senate seat, he'd just be one of a bunch of freshman congress critters (albeit the Republican that unseat a Democrat in MA). He's eked out a position that's very vocally anti-Trump, so I don't see any future for him in the current iteration of the party. In fact he was likely not going to get any party assistance even if he won the nomination... which was not guaranteed since 2021 Republicans are, apparently, all completely batshit insane.
In an interview the other day he joked about how he didn't really have many hobbies and needed something to do so his wife wouldn't murder him. I also think governing during the pandemic and during the Trump administration really took a toll on him, and I wouldn't be surprised if he flitted off to Tahiti or Guam or somewhere wicked fah dude and re-evaluated his life.