The simple answer is that conservatives are more likely to have more resources and to take advantage of that. The other is that they’re more likely to have hierarchical infrastructures that make it easier to engage the digital labor that’s needed to promote online activism. In other words, they tend to have more top-down organizations, and that’s just a more efficient way to distribute labor and get the message out.
In terms of the actual ideology itself, I do think there’s something about the nature of conservatism that makes it easier to promote online. Conservatives tend to focus on simple, clear messages around freedom in particular. The left tends to focus on this general idea of fairness.