Isn't this in essence the same as asking why did He make a variety of animals that have some shared characteristics? If they have shared characteristics, and he created DNA as his mechanism for allowing one generation to pass their characteristics on to the next, then it logically follows the DNA sequences would be similar also and the more shared characteristics they have, the more similar the DNA. Evolution is a possible explanation for similar DNA sequences, in exactly the same way that it's a possible explanation for similar skeletal structures, internal organs or whatever, but creationism fits these observations at least as well.
Or we could believe that God was deliberately making the entire genome of every species deceptively suggest an evolutionary origin, in order to test our faith.
I don't agree that the similarities in genome or anything else would suggest God was trying to deceive us. It's true that you could use evolution as an explanation for similarities, but as I pointed out, creationism would explain similarities at least as well.
I guess nobody at this site can understand genomics: Creation Scientists in the Biological Sciences
Both birds and flowers have pigmentation, but the molecular structures and biosyntheses of these pigments are very different. Why would a designer do that? Why use a completely different mechanism for making a red pigment in two unrelated organisms? After all, the result - a red color - is the same.
In many ways, Intelligent Design is a misnomer. If you consider the biome as a designed entity, there's massive duplication and waste. Why did the designer reinvent the wheel, many many times over?
If this list of people is meant to impress anyone, it's a sad effort. I've already mentioned that Gish doesn't have much of a record as a biochemist; in fact, his online c.v. has some very curious features. He was on the faculty of a medical college for a year, then went back to being a postdoctoral. Inquiring minds want to know what happened in that year; it's far too short a time for him to be denied tenure, and no one voluntarily quits as a faculty member and goes back to the lowly life of a postdoctoral. Damadian, as I've already posted, is a nut who tried to steal the credit for inventing MRI. I ran SciFinder searches on several of the others, and came up with no publications or a very small number. If this list is meant to prove active biological researchers can be creationists, I'm afraid it has rather the opposite effect.