Electron is large because it is a pack that combines full fledged web browser (WebKit) and server (NodeJS).

Web browser engine is designed with these priorities:

1. to provide safe browsing experience;

2. to present web pages in standard manner;

Note the order. Safe browsing means the following:

1. You must run user facing UI (tab) in separate process. This involves RPC with the rest of application.

2. You cannot allow any executable code other than managed JS. And so you MUST provide JIT or something like that as JS is the only option to run anything.

The order requires and leads to a lot of code to support those priorities.

And why would you doubt that? You used to be able to run a whole Linux distribution from a floppy.

It's not a complete alternative, so a lot of APIs and features that Chromium has are missing. The Chromium dev team isn't focused on size, but speed and features. While an alternative that does less can focus on size.

I didn't say I doubted it.

I mean why would you think there is something that requires explaining.

It doesn't do this.