why PDEtools:-Solve fails to same two equations in 2 unknowns when solve can?

restart;

interface(version);

Physics:-Version();

libname;

restart;

eqs:=[-2*arctanh((_C1-1)^(1/2)/_C1^(1/2)) = _C2, 0 = _C1^(3/2)*tanh(1/2*_C2)*sech(1/2*_C2)^2];
unknowns:={_C1,_C2};

sol1:=solve(eqs,unknowns);

sol2:=PDEtools:-Solve(eqs,unknowns);