This is a funny sentence… Tomoyo became selfish by forgetting about her goal?
Tomoyo never became selfish; she always was selfish. Her goal of saving the Sakura trees is both an inconvenience for the development of Hikarizaka and a very selfish usage of her position’s apparent power.
It’s contextual. There’s an implication that, if her struggling family came together to see those trees once upon a time, and if Tomoyo is trying to keep those trees around, then her family is still very much fragile. Saying “I want to see them one more time” is the same as saying “I want my family to be together for one more day.”
The goal itself, of saving the trees, is some twisted contrivance Tomoyo has formed to keep her life and her emotions stable. Without it she’d just be a delinquent like Tomoya.
I wrote a giant blog post about exactly this topic—Maeda is a manipulator of filler. To quote myself:
He still follows the Tactics formula, but he includes a patterned comedy-drama-comedy-drama structure, with the initial drama being a warm-up of sorts, and latter drama being the big emotional one. Sometimes there will be a handful of smaller dramas before the big concluding one, and sometimes he’ll only include one. The frequency and amount of dramas dictates the atmosphere of the story, slow & chill or rocky & stressful being the two extremes. This style of short conflict allows Maeda to control the pacing of his story easily without having to alter other parts of the story to match.
It could be argued that the entire route is filler; even the drama is meaningless when zoomed in on. The notability of the route comes when you zoom out and look at the entire timeline. All those individual moments are but building blocks placed to manage the structure of the greater narrative.
It’s very much intended. This same idea of a flawed character is present in literally every story Maeda writes (though the degree to which he disguises it varies.) Every route he has lead, every track in Love Song, every episode of anime. It’s all about failure.
A big part of Tomoyo’s character is her search for an idealised version of herself. Her idealised self does everything for a greater good, or for a big emotional purpose, because she’s constantly afraid; she’s afraid of losing people and she’s afraid of looking imperfect…
Realistically however, Tomoyo gets led around by whatever emotion she is feeling at the time. She will do everything in her power to achieve a goal, but her goals change in a heartbeat. One second she’ll be doing everything to keep someone close to her, and the next she’ll be overcome by an “ideal” behaviour or circumstance. It makes sense that she’d be such an unstructured personality when you recognise her unstructured upbringing.