If the computer is compromised then malware with sufficient elevated rights can compromise the software wallet. If the software wallet itself is badly crafted, which you can't check with closed-source software, then you're screwed anyway.
Other wallets might also get compromised if the computer is compromised. Even if someone has access to your wallet, I don't think they can access it unless they can crack your password or have private keys. Since it's only happened with Atomic users (we did not see the same reports from other wallet users yet), I guess OmegaStarScream might be correct. They might be fallen for phishing. But according to Atomic Wallet, 1% of their monthly active users reported that their wallet is drained. So, If their active user is 100K, 1K users' wallets were compromised. I don't think that many users could fall for the phishing trap.
Atomic might be hiding something about
how are the private keys generated and them being non-custodial. I was using Atomic Wallet 2.45.1 For a while. Luckily I had nothing in my Atomic wallet, and I just uninstalled their software in case it contained any virus. Many users screamed in their tweets and complained about how much they lost. I am afraid now. I moved from Atomic to Electrum a while ago. I hope Electrum is the most secured and trusted among others!