Electrum is not a platform, it is an open source desktop/mobile wallet "released under the MIT License", and the main reason why people use it is that it is free and fairly easy to use. What most people don't know is that such software is subject to code changes and that anyone with a little understanding of programming can make a fake wallet and distribute it over the Internet.
No matter how secure the crypto wallet was, keeping 1400 BTC inside just one wallet is a stupid move - if I had 10% of it I would divide it into at least 5 different and independent wallets, and thus diminished the risk of losing everything in one bad move.