From this almost infinite all possible mutations (1 mutation of nucleotide in given sequence, two mutation or 10 mutations but on different places etc...) only one was picked by natural selection. All others should be detrimental while weren't picked.
This is a baseless assumption. Just because only 1 particular beneficial mutation ocurred and was subsequently selected doesn't mean that that was the only mutation in the whole available genetic phase space which could be beneficial and it certainly doesn't mean that all others would be detrimental.
Indeed and it is now constituted of something like 1,400 species. Not too shabby really since the class Mammalia only has something like 5,800 extant species and arose during the Triassic.
TTFN,
WK
Edited by Wounded King, : deleted excess 0s and revised title