The hypothesis of 51% attack is based on a malicious entity is able to control more than 50% hashrate of all mining nodes. It's understandable that there's huge amount of mining power existing nowadays, however, they grew up gradually since 2009.

I'm wondering when there were only a few of people who knew the bitcoin back to the 2009, therefore, surpassing 50% of mining nodes was fairly easy(for instance, assuming there were only 10 participants in the early days of bitcoin). Because controlling more than 50% of mining power probably just needed to control more than 10 computers in the earliest days since bitcoin birth.

As a result, do I need to worry about the 51% attack possibly happened in the blocks of which the height number is small and are those blocks trustable?