This was their announcement regarding the closure:
This was on 2020/06/15
Dear users!
We decided to close Rahakott wallet.
Rahakott will be working until 1st of August 2020, all funds will be available for withdrawal. Signing up will be terminated on 1st of July 2020. After 1st of August, all information will be destroyed and the wallet will stop its functioning. We ask our API users to transfer the work to other services.
Thank you for spending these three years with us, trusting us and suggesting how to improve wallet functioning.
We wish you success in your work and good health.
This was on 2020/07/26
Dear users!
We announced the closure of Rahakott on 15th of June 2020. We remind you that Rahakott wallet will stop functioning on 1st of August 2020 and you will not be able to withdraw your funds afterwards. We have decided to take the following steps:
API will stop functioning on 28th of July 2020
Mixer will be switched off on 28th of July 2020
Withdraw your funds until 30th of July 2020!
Source
I think their voluntary and quick closure was probably fueled by the fact that they also had some sort of mixer service just like what happened to bitblender. Maybe they smelt a rat about being investigated and didn't want to end up like bestmixer.io