Re: Adobe, masters of the trend
For a second I was going to say that Flash had been popular for a *long* time until its recent decline (*). Then I realised you really did mean sites that did literally *everything* within a single Flash blob- title, menus, content. All Flash, no HTML I'd almost forgotten those...
IIRC that peaked circa the early-to-mid noughties(?) I remember applying for jobs at that time and being annoyed at how companies- including banks- were creating self-indulgent style-over-substance websites that were obviously meant to impress, but a PITA to use in practice, e.g. non-browser-standard user interfaces, breaking the browser's own back button, etc.
Flash remained for more appropriate uses, but- as you say- that specific trend thankfully died off.
(*) Probably from the late 90s until the past few years when the rise of the Flashless iPhone and HTML5 put the writing on the wall. But you can't deny it had a long run- in essence it became what Java Applets were supposed to have done (but failed to do because they were too bloated for late 90s computers)- embedded rich content *within* websites.