Some questions which anybody might have about this case.
Q Why was he prosecuted if the evidence clearly points to another person?
A The main reason was probably simply that the FBI and police did not want to admit they got a confession from the wrong person. A lot of law enforcement relies on extracted confessions, and, in the United States, an art has been built around getting people to confess to crimes they did not commit.
Another factor may have been religion. Esar Met belongs to a less popular religion in the United States while the obvious real suspect is more mainstream.
Q Is it possible neither Esar Met nor 'roommate #1' is the killer?
A Very possible.
There were two roommates who moved out of the apartment shortly before Esar Met moved in. They are never discussed in the media nor at trial, aside from a passing reference by 'roommate #2', the brother of 'roommate #1', who says he and his brother moved upstairs when those two moved out.
Another possibility is that a law enforcement officer, or a team of them, were involved in several child murders in that region.
Child abductions of this kind are extremely rare, about 100 a year, and the vast majority involve 'children' in the 15 or 16 year age range. A significant percentage of all the very young children abducted nationwide have been abducted from that area, a very high number relative to the population.
One thing that should raise questions is the fact that a higher percentage of the victims and suspects are from outside communities. Rosie Tapia was Hispanic. Hser Ner Moo Burmese. Terry Lee Black is Hispanic. Esar Met is Burmese.
In other words there are a high number of very young children murdered in that area, but both the children and the suspects are outsiders. This could tend to indicate that a local person or people are committing the murders then pinning them on outsiders. These populations, Burmese, Hispanic etc have a very low level of this type of crime everywhere else where they live.
The people most able, and most psychologically likely, to commit that kind of crime and pin it on others would be a small group of law enforcement officers.