They lost all emails recently, and as per the other comments they were limiting their funding options.

In addition to that, their pricing was very expensive with a sub-par experience compared to Protonmail, which has improved massively in the last year.

https://cyber-privacy.net/ctemplar-catastrophic-incident-wit...

`CTemplar said they were “actively refusing investments, donations or grants from governments and corporations.” This clearly turned out not to be viable, at least in this case.`[0]

This sounds like as good an explanation as any.

[0]https://reclaimthenet.org/private-email-provider-ctemplar-is...

To be honest, my question would be why this wouldn't have happened. Their cheapest plan was more than Fastmail Professional - while delivering less product than Fastmail Basic and not having anything approaching the Fastmail brand. I have a hard time understanding why anyone would have used their service.