How to make bitcoind connect to more nodes?
Bitcoind will never make more than 8 outgoing connections. By default, it will allow up to 128 connections (see -maxconnections), but that includes incoming ones.

Available connection slots of fully synchronized nodes are a limited resource on the network, so they shouldn't be wasted. As long as you have enough connections to be sure that at least one is not trying to attack you, you should have enough.