Riding a trend is one thing, but it's an oversimplified way of looking at the situation. Trends are always on the way up or down, but plenty of blogs have found sustained success. Let's look at two different scenarios.
When AdEspresso published its first blog post in September 2012, Facebook reported that its annual ad revenue was $6 billion. In 2018, Facebook is on track to leverage its 1.45 billion daily active users to earn more than $40 billion in ad revenue. The Facebook Ad platform has absolutely exploded.