Let me know the first bitcoin address with just a's following the 1. Even attempt to make it it would takes ages
1aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa Natural, sure
Your error here is confusing something that is random a bitcoin address with something that is not random the end of a viral genome. The end of a viral genome cannot be random as it must serve a very specific functional purpose.
All known infectious retrovirus DNA sequences end with a series of repeating nucleotides called a long terminal repeat (LTR).
For your further reading and knowledge:
Function of the retrovirus long terminal repeat
https://www.sciencedirect.com/science/article/pii/0092867482903671