Steal Someone's Thunder Meaning

Example : 1855, Jno. E. Vought, “Editor's Table (letters)”, The Knickerbocker: Or, New-York Monthly Magazine Volume 46, page 101:  There are several upstarts, who, without the genius to invent a style, have been copying yours, and trying to steal your thunder.1898, Boot and Shoe Recorder - Volume 33:  It also serves to give someone else an opportunity to steal your thunder if he considers there is any amount of thunder in it.