When Google Plus (also known as Google+) launched in 2011, some optimists thought it would eventually threaten Facebook’s social-networking crown. Four years later, the general perception is that Google messed up its most aggressive attempt to break into social. Why did the world’s biggest search engine fail to become the world’s biggest social network? According to Mashable, which interviewed a number of people involved in the project, it all came down to a few (relatively) straightforward reasons. Let this be a teachable moment to anyone working on a big tech project.

No Product Differentiation

Although Google Plus had a lot of cool features, none answered a central, burning question: Why should people use it over Facebook, a service that seemed to already please many? When building a product—whether software or hardware—you need to figure out a compelling reason why people will want to use it. Does it accomplish a task faster than anything else on the market? Does it offer a new, better way to solve a problem? Google Plus never answered those sorts of questions in a definitive way, and suffered for it.

Remember: Strategy, Then Action

In Mashable’s telling, Google was so desperate to build a Facebook killer that it immediately cycled up a massive team tasked with getting things done fast. That turned out to be the wrong approach. Launching into action with a half-baked strategy is a really good way to produce a half-baked product. Even if you’re under significant time constraints, make sure you’ve thought out all your features (as well as your strategic contingencies) before making a move.

If It Ain’t Broke… Don’t Break It

Google’s decision to make Google Plus the glue uniting its various services, including YouTube and search, must have seemed like a good idea on paper, but led to protests. Critics argued that using Google Plus to comment on YouTube videos exposed real names, provoking privacy concerns; others saw the introduction of Google Plus content into search results as a sullying of the latter. While the insertion of Google Plus data in search results was always opt-in, it sparked one of those reputation-dinging fights over privacy and security that Google always likes to avoid. Google eventually rolled back its stance on YouTube integration, but not before alienating a healthy percentage of users. While it’s pretty much impossible to avoid all controversies, test whether an audience will go for your latest feature or term-of-service before you roll it out—that could allow you to avoid unforced errors.

Pivot Quickly

Google has only recently begun making fundamental changes to Google Plus, orienting it as more of a photo and communications service than an outright social network. That might help preserve some of the core features that engineers toiled over for years, but it won’t rehabilitate Google’s reputation as a company that tried to dominate social and lost. Could Google Plus have done better if Google had chosen to pivot more quickly? That’s an open question. But readjusting strategy in light of analytics that suggest your current strategy isn’t working is generally a good idea.