Because it's terser
Modern English prizes brevity and clarity in expression. There's no reason to elongate the phrase into the password of the BTC wallet of the company and several reasons not to.
The 'rule' you were taught and linked to is balderdash. The ESL teacher was misunderstanding/simplifying this prescriptivist rule that 's should go with things that are vaguely people-like (inclusive of animals, companies, organizations, countries, personifications, &c.)
No one at all pays attention to that 'rule' and people use possessive 's for animals and inanimate objects constantly. Of course, don't bother challenging your teacher or fighting with the person who grades your papers... but don't be surprised when you see this construction.