This aligns with what (little) I know about this historical period. For an accessible – albeit fictional – depiction of the collapse of 5th-century Roman Britain, Stephen Baxter does a good job of it in Coalescent¹. In the first part of the book, he describes how the crossing of the (frozen) river Rhein in 406² precipitated the political and economic destabilisation of Northern Gaul and then Roman Britain.

The focus on the Crossing of the Rhein and the Romano-Briton contenders for the throne seemed a little too conveniently dramatic. Having said that, I haven't read any more scholarly books on this period of history that contradict Baxter’s narrative and reading Coalescent book was a great way to learn about the various factors that caused the collapse of the Empire on the western fringes of Europe.

¹ https://en.wikipedia.org/wiki/Coalescent

² https://en.wikipedia.org/wiki/Crossing_of_the_Rhine