Maybe it’s becoming more normal, or at least it’s a trend I’ve seen a lot in the past year or 2.
In finance there is a big push to go ‘digital’ which creates a lot more change and requires a lot more people. Good people are hard to come by and are getting poached. Companies are now paying a lot to stop good engineers from going to tech or rival companies. It’s actually a great time to change jobs for a pay increase IMO.
The team could also be stagnating, eg they were on the up a few years ago and now things are different. Maybe the product they’re working on is not being perceived as well, wasn’t successful, or the people who built it originally are not interested in maintaining.
There could be a few other possibilities as well, like the environment being terrible or bad culture due to tech debt, too many prod issues and firefighting constantly, backward processes.
If people start leaving though it’s very tough to fix things and make it better. Anyone decent will also get disenfranchised and move on too. It’s definitely not normal for such a high turnover in a high functioning team though.