Why you need to use ~4gb assets for your game? The size is just too large for web browsers to handle it even on the latest powerful desktop. Construct 2 is not means to create triple A games, it's designed to build games that're manageable on hopefully every platforms.
The problem is now you load 300 megabytes of sprites into your web browsers, which end up your system's free memory is even lower than the game needs. As a result, your sprites don't even load into memory and rendered to the screen.
Remember not to waste your memory.