I think you misunderstand the Network part of the Lightning Network. It is not necessary for users to have a direct payment channel to Wikimedia in order to donate to them. They just need to have an active channel to anybody in the network who is capable of routing a payment request to Wikimedia's node.

The assumption is that Lightning users already have active open channels to other nodes in the network, and so making a new donation to Wikimedia would not require any additional channel opening, and no on-chain activity.