As mentioned there's kinda quite difference between the Anime and the Manga, once we will realise what made the the difference we will also realise that there's no difference.
In the Manga, the creators gave Light hell of humiliating death, after Light shout to everyone he knew and trusted (like in the anime) he's asking from Ryuk to write his name in the Death Note and then he's dying begging for his own life, but before the part he's shouting to to Misa and Takada, he's also shouting to Mikami, and he's responding, unlike the anime.
Mikami part in the Yellow Box wear house is ending after this, and in the last chapter it's been said Mikami had been suicide while in jail.
In the Anime on the other hand, to give Light much more less humiliating death, when Mikami sees Light lies in his own blood, he's stubbing himself with his own pen, the part where he talks to Light however is cut, the only clue to see his own feeling is this scene.
Except for Mikami suicide letting Light ran away from the ware house from his pitiful death in the manga, we can assume something much more that that scene - Mikami is so disappointed from Light, he was his god for every meaning, his psychological shock from sees his god roll-in in his own blood, gave him big mental shock - how can be his beloved god can be so humiliated? MadHouse clearly wanted us to understood that from that scene, in fact, his suicide scene in the anime make much more sense in the psychological way than in the manga, he dedicate his life for believing that Light is god and then he sees his own beloved "god" swimming in his own blood, there's no bigger mental shock than this.
To come and say that the anime cutting that scene for make Mikami not disappointed is exaggerate, Mikami sure looked disappointed from Light when he denied him, but after that Light talked to him about his mistake so he may regain his faith in him, but saying Mikami made suicide to let Light ran away is also exaggerating, human that reached to level where he decide to make suicide usually make those awful choices from hating their own lives and depression, not from some kind of "I will suicide to let him ran away", especially not from the look of Mikami before his own suicide, he clearly were not only disappointed from Light, but felt disappointed from his life for dedicating it for that god that swimming in his own blood, and I think it is clear enough.
Conclusion
- Mikami did disappointed by Light at the end and didn't believed in him, and not only that but hated himself for following such "god", he killed himself.
- Though Mikami's suicide benefit Light to escape, it only made by MadHouse to create different ending than the manga where Light died less humiliating.
- It's unthinkable to say that Mikami made suicide to benefit Light to ran away, because even if it is, it's not 100% that Light would succeeded doing this, to risk your life for someone who just terribly humiliatingly lost and disappointed you for such low percentage of running it's too exaggerating, even for Death Note.
