So if you consider the fact that Grantaire probably met Enjolras around his 20th year ( we learn Enjolras is 22 when he's first introduced and les amis seems well established enough to have been around for awhile ) and he died when he was 26. So Paris / Grantaire really only knew him for about 4 to 6 years. Amazing he's still so upset 184 years later, Enjolras has been dead for 10 decades, a century and a half!
The less serious answer to this is: yes but dem buttocks
The serious answer to this is probably something on the lines of: Grantaire/Paris was suffering from a horrible build up of mental issues including PTSD, depression and alcoholism (though he wouldn’t have known what those were. He was very much “I’m just useless and a bad person”) from actual centuries of war, inner turmoil, poverty, the terror, Napoleon & Napoleon’s fall & the resulting invasion– all of which he physically felt the affects of and was kicked off by Jeanne’s death and the following trauma. Not to mention the Grantaire/Paris thing and repression of his cityhood, the loss of his family when he went into hiding. Enjolras (and the other Les Mis! Their deaths were just as impacting!) seemed to be a guiding light at a time when he desperately needed it. Yes he loved him, but perhaps he also wanted Enjolras to save him. And when for the first time in centuries he felt hope, it was taken away from him in the most brutal manner possible. By his own people. This was less ‘he lost one guy and is still upset??? it’s been ages!!’ and more ‘Paris has had a tremendously shitty life and Enjolras’ death was the breaking point. After that Paris had a complete breakdown, all of his mental issues were ripped open and intensified, was totally overcome by the thought of still living as he did and Atlantis absolutely took advantage of that. and now Paris is lost, grieving, drowning under centuries of trauma and unresolved issues and still in an immense amount of pain while under the control of an absolute monster who wants to keep him that way’
but yeah. only knew enjolras for a few years. why is he being so dramatic. let’s go with that.