buy into something
— phrasal verb with buy us/bɑɪ/verb [ T ] past tense and past participle bought /bɔt/
to buy a part of a business in order to have some control over it:
They bought into a software company.
If you buy into an idea or plan, you give it your support or agree with it:
Parents are expected to buy into the school's philosophy when they enroll their children.