Sterling most definitely lost subs due to their transition. That does not explain the continued bleeding, or at least it doesn't track with other examples of mass subscriber loss over an individual event. That either means bigotted viewers were just finding out about it (which means inactive subs, which is awful for the algorithm), or the content is less desirable than it once was and the initial sub loss ended up being a snowball event (which is awful for the algorithm).
Either way, stuff like this is usually a death knell for sizable channels, or at least indicates a major downsizing. Any kind of multi month-long sub loss leaves a channel irreparably fucked by the algorithm without a massive event to counteract it (presenting proof to invalidate accusations for example), which means you won't see those videos recommended to new potential subs. Sterling will continue to get good engagement and views and will remain rich thanks to Patreon, but their voice in the community is going to be no where near what it once was.