As more and more competitors entered (especially in less defensible product categories), store shelves became more inundated with more choices than you (the consumer) could even process. Making a brand choice became less straightforward, and as more and more brands put out their messaging, the more confusing the noise became.
To make matters even more complicated for brands, the advent of digital and social media initiatives meant that getting mindshare no longer involved big TV budgets. Word of mouth, which has always been able to make or break your marketing efforts, now can spread faster and further than before. Moreover, customers trust each other more and brands less, per Edelman’s trust barometer, and to really move the needle, you increase awareness via brand advocates, not your own messaging.
See the article about building customer loyalty