The current idiomatic way of doing web layouts was, back then, almost entirely theoretical. The reality was a cross-browser hell filled with onResize listeners, in turn calling code filled with browser-specific if statements. Entire JavaScript libraries were devoted to correctly identifying browsers in order for developers to take appropriate measures when writing UI code. Separate machines specifically devoted to running old versions of Internet Explorer had to be used during testing and development, in order to ensure end user compatibility.
In short: The web was not in any way, shape or form more convenient for developers than the RAD tools it replaced. But it was instant access multi-platform distribution which readily allowed for Cloud/SaaS subscription models.
Electron happened more as an afterthought, when the ease of distribution had already made web UIs, and hence web UI developers, hegemonic. Heck, even MS Office for the web predates React, Electron, and something as arcane as Internet Explorer 9.
Things have gotten much better, but we're still having to reinvent things that just existed natively in VB6 (DataGrid, anyone?) - and at the cost of increasingly complex toolchains and dependencies.