Think about it, though. Enjolras was never really around when R made his more socially concerned rants. The fact Enjolras was seemingly surprised that R was well read when he offers his help attests to this.
Enjolras probably had no idea about R’s knowledge of poverty in London, his concerns for underprivileged children or his disdain for American slavery. He was probably unaware of why Grantaire was so cynical beyond being a sceptic.
He didn’t get to appreciate R as a multi-faceted being until the very end, and he evidently liked what he saw.