Viruses even when i have Avast

I rec’d a notice from google that i had 4 viruses threatening my Stylo 3 and SIM card. I had Avast security at the time. I installed another program that said it cleaned 2 viruses. Neither Avast nor this other program found the other 2. I can still not find the info from Google to let you see it. My phone had acted up before the removal by typing what it wanted to and going between people on Messenger and attaching photos and/or maps to messages. Why didn’t Avast catch the viruses?

https://forum.avast.com/index.php?board=66.0

Why didn't Avast catch the viruses?
No security program have 100% detection or zero false positives