On August 6, 1991, Tim Berners-Lee launched the world’s first website, which is still live today. Over the years to come, many more websites emerged offering users information with bare-bones usability and optimization. A few years thereafter, major competitors like Yahoo (1994) and Google (1997) entered the scene to improve and simplify how data is indexed and delivered.
With search engines becoming household names and more families becoming connected to the Internet, finding information came with greater ease. The problem was the quality of that information. While search engine results matched words from user queries, it was usually limited to just that, as an overwhelming amount of site owners took to keyword stuffing (repeating keywords over and over again in the text) to improve rankings (for which there was no criteria), drive traffic to their pages and produce attractive numbers for potential advertisers.
In this primitive stage of SEO, anything goes. There was also a bit of collusion going on. In addition to the keyword stuffing, people were using excessive and "spammy backlinks" to improve their authorities. Not only were there no ranking criteria at the time, major algorithm updates would take several months to complete, allowing black-hat SEO tactics to remain effective for long stretches of time. Also by the time search engines fixed algorithms accordingly, there were already new black hat SEO practices taking place that the fixes didn't address.
Back in the 90s marketers would routinely keyword stuff the heck out of websites, because, well, the more times a keyword appeared on the page meant the more relevant and likely it was to rank well in these early search engines.
Search engines do not just look at the content of the page; they also look at the number of links pointing to that page from external websites. Back in the 90s there was no ranking of these websites, so bascially you could actually link back to your website from virtually anywhere. One common practice involved submitting your website to web directories and getting a link in return. Others signed up for free acconts on forums and free webpage builder pages such as GeoCities, and just spammed those sites with backlinks back to their website to help ranking. Guest books were also widely abused for spammy backlinks.
Back in the 90s, content marketing was simply overwhelming. There were mounds of backlinks piling up to rank higher in the SERPs, an unwavering dedication to tagging pages with an excessive number of phrases and the all-time favorite: keyword stuffing; the end all be all of digital marketing. It seemed as though every other word on the page was a key phrase, sending readability and user experience to an all-time low. In the early 90s, traditional marketing took precedent over digital based solely on the low number of consumers with access to the Internet at that time.