Yahoo's roots were actually in a rejection of engineering.
For years their primary product was their human-curated directory of Web sites. It was popular because the quality of results returned by the algorithmic search engines of the time (HotBot, Lycos, AltaVista, etc. -- you young 'uns in the crowd may need to look them up) were so poor that you had better odds of finding what you were looking for in Yahoo's directory. The directory left out vast numbers of sites, of course -- that was the cost of trying to manually maintain an index of the Web as it exploded in size. Human curators couldn't keep up with that growth; only software could. But Yahoo bet that software would never be as good as humans at finding the site you were looking for.
Then Google came along and built software that could index the whole web and return relevant results from it, and that knocked the bottom right out of Yahoo's manual-curation approach.
I worked at Yahoo 2003-2005, and back then I used to tell everyone who would listen that a big part of the problem was that the engineering team at Yahoo believed that Yahoo was a technology company, while the product team treated it as a media company.
It was an ongoing tension while Yahoo was still desperately clinging to the fantasy of regaining the search leadership, or at least stopping Google in its tracks - search was to a large extent Yahoo engineering's claim to legitimacy for the idea of a tech focused Yahoo.
Without it, what was left were mainly support functions for a massive content operation, but with a team still to a large extent seeing itself as the core of the company.
Yahoo wasted tremendous amounts trying to do technology for the sake of being a tech company rather than to support revenues; a lot of little fiefdoms in engineering were allowed to exist seemingly because it looked internally like Yahoo was building an impressive technology base, while it often instead was creating tensions in the business and costing ridiculous amounts.
