Not surprised - Mars has an ice cap or sorts and many canals and canyons so it’s been well known that mars had water on it at one point which would make basic chemical precursors like these likely.
But it’s still not known if life ever actually existed on Mars before whatever cataclysm befell it.
The existence of methane on Mars means nothing in regard to the existence of life forms. The atmospheres of the outer planets contain large amounts methane, ammonia and other organic compounds. That’s either a natural process or a lot of farts.