I don´t think Ostrava offers some special conditions. The main problem is the captive population in Europe itself. Male-scewed, many animals too old, incompatible pairs, and part are hand-reared animals who seem unable to breed (probably not able to form cohesive pair that would copulate).
Captive population in Europe is probably already functionally extict, due to past mismanagement and some bad luck. Unless the US would donate some young animals.
And here a video about money fundrising for wild Sclater´s lemurs, including eng subtitles. Neat to see many children participating.