Filesystems which store and manage your files, can be diveded into 2 categories: Case sensitive and case insensitive. On a filesystem (FS) of the first categories
FoO.BAr refer to different files, while on a FS of the second both names point to the same file. An example for a case insensitive FS is NTFS, which is the default on Windows computers, and hence Windows users are accustomed to its behaviour.
Cryptomator provides a custom FS to efficiently encrypt your files and never store your data unencrypted on “cold storage”. Everytime a vault is unlocked, this FS is used and only integrated into the surrounding OS. When Cryptomator was founded the decision was made to implement this encrypted FS as case sensitive. And, well, therefore, every vault is case sensitive meaning also on Windows systems. This decision cannot be simply undone, since it would break existing setups.
To alleviate this situation a little, when you use Dokany on Windows, the search in a vault is not case sensitive. But to address a specific file/directory by its path, you still need to get the casing correct.
You might have now the question, why not adding an option to ignore the case for a vault. An answer can be found in the following disscusion on our issue tracker: Same folder exists twice first Char lowercase and uppercase · Issue #622 · cryptomator/cryptomator · GitHub