My understanding is that Ryujinx has been a lot more cautious in general. When TotK was leaked, simply mentioning it in their discord instantly got you the pirate role (which means they won't give you any sort of support), and continuing to mention it got you a ban. Similarly they crack down hard on even the slightest mention of title keys or the like. They're very upfront that this is done solely for legal reasons, but they're also extremely thorough about cracking down on any discussions that could expose them to legal vulnerabilities.

They're more cautious in a few other ways, too. They have a patreon but you don't get any newer versions or improved features through it, just cosmetic Discord roles, whereas Yuzu offers the latest releases to Discord subscribers first.

Both of these things (Yuzu devs and moderators openly discussing how to get title keys in its discord, and the fact that they profited off the TotK leak by locking versions updated to support it better behind donations) were specifically mentioned in Nintendo's lawsuit, so it's likely that Ryujinx being more cautious around potential legal vulnerabilities is what kept them off of Nintendo's radar, at least for now.

(Of course, if Nintendo does well enough against Yuzu here they might move on to Ryujinx next - but it makes sense that they'd go after the easier target first.)