Can anyone explain the ‘FDIC or ISPC’ insurance on Vanguard ??

Hello everyone ! I Don’t think I have ever posted here but this sub is why I got interested in low cost index funds about 7-8 years ago. I thank you guys’ for that. Anyways, Currently I keep about 80% of my money (500K) in vanguard ETF’s. Me and my wife have a separate combined income brokerage account in E*Trade account we both contribute to. My question is - Is there any reason I should start making my same contributions in another account as opposed to Vanguard, like Fidelity or Charles Schwab, because I may be over the amount I am insured for? Does this make any sense or am I an idiot? Keep in mind, I have extremely little knowledge on what I am actually doing here. I have just been contributing pretty heavy and the gains keep coming. Thank you if you are able to simplify this for me !