I think a lot of us forget just how vast YouTube really is. So many thousands of videos are being uploaded every day that, even if YouTube wanted to promote smaller channels, what is the criteria? Do you want to promote a channel that is very excited about making videos this week, but gives up next week? A channel that has a cute video right now, but then might start posting problematic material tomorrow? Channels that present material that may be copywritten to others? It's a tricky proposition.
So yes, there is a bias towards larger channels in the Trending section, but I think, outside of the business reasons for that (more views means more money, and known quantities means more guaranteed views), there's also the fact that it's just impossible to promote small channels without making decisions that would take an enormous amount of effort to maintain. So there's the related content videos that pop up next to all videos, and those, while not totally democratic, do tend to feature small channels pretty regularly.
Overall, I think that YouTube is one of the more democratic platforms out there. You have as much chance of being "discovered" as anyone else, and if you are patient, you tend to get somewhat of a following if you're consistent and make a lot of stuff.