I've let some gear go as well. The E-M1 is gone, as are the 45/1.8 and 75/1.8 in m43 mount. The E-M1 was really only needed if I was going to run a 2-body m43 kit, and with those lenses gone I didn't have as much of a need for that. The 45 I let go because I barely used it at all. It's a REALLY good lens, but for the way I shoot the 12-40 at 40mm simply works better. The 75 I used as a faster alternative to the 40-150 f4-5.6R, but while the results were amazing, I always found it either too long, too short or too limited in MFD. All 3 of these went to get the Tamron 70-300, which is one half of a 2 lens Sony hiking kit.
The other lens is the Zeiss 16-35/4. I'd originally planned on getting the Tamron 17-28/2.8, but I was able to get a much better deal on the 16-35 and when working with only two lenses that 28-35mm range will give me more flexibility than f2.8 will for what I do. Biggest downside is the 16-35mm is 72mm filters while the 17-28 takes 67mm filters like the 70-300. I'm shooting these on my partner's A7II for now (actually, I expect she'll get the 70-300 long-term to replace her current telephoto, a Canon 75-300 on an adapter, I'll likely switch eventually to a 70-200/4)
For now, I'm not getting out of Micro 4/3rds. I've still got the E-M5II and 3 lenses, the 12-40/2.8 (which I love), the 17/18 (my webcam lens, also a nice street lens) and the 40-150R (the plastic fantastic of consumer telezooms).
As to why Sony, well there's two reasons.
1. My Partner already shoots it. We can share gear and for now I can just use her body, while she can use my lenses when we're out together.
2. All sorts of neat stuff available. Sigma's I series lenses, Sony's G compact primes, Samyang and Viltrox AF lenses, TTArtisans and 7Artisans manual lenses, etc.
I do like the Nikon bodies in my price range better, but the Sony ecosystem just works better for me right now. Of course, I could just get an AF adapter and use the Sony lenses on a Z6 or Z7 in the future. Who knows? It's not like I've settled on a body for myself in E mount yet, although it's basically down to an A7III or an A7RII at this point.