People who say you're selling out are being silly. Be yourself and try to make some entertaining videos, feel out what people want to watch. You don't have to suddenly seem like a different person to go from being serious to being more silly, it's more like a change of tone and mood. It isn't like you're changing your opinion, attitude, or anything. You can be light-hearted and be cynical (if that's your thing). Your videos seem like they have an intellectual, philosophical quality to them, where you're thinking really hard about what you're talking about. That's a great type of video that a lot of people seem completely unable to make, because they aren't in touch with that side of themselves.
Everyone has different sides to their self, different moods, different tones and perspectives that they can feel toward different subjects. Personally, my attitude toward everything is to find the humor and silliness in anything. However, I can be in a more introspective, critical mood, which people wouldn't find funny. These types of videos aren't really meant for entertainment, but more like for thinking about different perspectives, or simply agreeing with whatever the author of the video thinks.
TL;DR: You aren't selling out or anything like that if you're using a different tone/mood. If it doesn't feel like you're pretending, you aren't pretending.