You have a point there, but Google's profits from Android are at least one order of magnitude larger than the numbers you quoted [0], and it may be rational for them to risk the fight.
Maybe, but the counter is enough money is at play to create a successful competitor. Someone doing a smart phone with 1/10th the penetration of Android is somewhat significant and not to be ignored. (in absolute numbers that is more than the number of Mac users vs Windows users)
[0] https://www.kamilfranek.com/how-google-makes-money-from-andr...