Both mentioned mixers invested a lot of money in the development and promotion of the platform, certainly, they were considered reliable. Although they did not announce the reasons for exiting the market, we all assume why it happened. I'm pretty sure if there weren't certain 'SEC' events some of them would still be operational.
I don't know why, but whenever I see a mixer service disappear without letting its users know that they are going to stop providing their service, I always think it's an exit scam and they never had good intentions. I never managed to understand how mixers get seized by the Government and what technology they used to seize those mixers and arrest the owners of these platforms. I always felt like most of them are just exit scam and some of them were seized by the authorities.
You are very correct and I have to completely agree with you, after the take over and closing down of chipmixer which was evident and verifiable to the general public, some mixer developers and management have seen this as one of the easiest means of exit the market quietly without making alot of noise.
The chipmixer incident have opened the doors to other mixers to sometimes, even comoflage and make users believe they have been seized by the SEC, making users to simply move on and don't scream scam.
In the case of unjoin and tumbler, my instinct tells me this two mixers in particular performed a scam exit, (except there is any evidence to prove otherwise), including one other mixer that did close down few weeks after the sec seized CM, and even changed their website to make look like the sec really took it over.
Why I said tumbler and Unijoin performed a scam exit is because, if truly they were seized by the sec, same sec would have also come after mixers like mixero, thormixer, coinomize and the rest.