Descritption: Equations below won’t display in two lines, but in one, after rendering. It against MathJax or Latex syntax, and I can’t find any way to break the line when I write math equations in Obisidian. Is it a bug or unimplemented feature? Or i just use it wrong?

For me it’s not a bug, it might be a misunderstanding of maths in LaTeX. You cannot have two equations on two separate lines like this. If you have a system of equations, or some set of equations, it should be written like this:
$$
\begin{align}
1 == 1 \\
2 == 2
\end{align}
$$