Honda were a deeply introverted company. NIH - Not Invented Her - described their philosophy.
An unwillingness to adopt the ideas of others, coupled with poor financial returns post the 2008 crash, meant they had less to invest.
Something had to give - and it was Europe...
Honda may have been introverted, but have pretty much been at the forefront of auto engineering, so why would they need the ideas of others ? The Americans in particular took to Honda in a big way, practical, efficient sporty cars with bulletproof reliability, also very popular throughout Asia.
Honda were the first major car maker to refine electrical power steering system to full electronic control - in 1990 it was fitted to NSX. Suzuki used an NSK EPS system in 1988 but it was very crude and unreliable.
Honda are still the 5th largest car maker in the world, and have always gone it alone, now they have a tie up with GM which could yield many savings in R&D costs in increasingly hi tech cars.
To look at Honda only in Europe is to miss the bigger picture, their market share in Europe has always been around 2% or less. Honda was very slow to adopt diesels because they realised that as far as emissions was concerned diesels would never be anywhere near clean enough. This basically closed off the company car market in Europe to them, where Diesel was supported by governments and benefits in kind tax relief was higher on diesels - and that has been proved by Dieselgate be a major policy blunder ( but diesels were pushed by European makers, and never popular in USA except in tractors and lorries ) , and Honda were correct.
https://www.carlogos.org/reviews/largest-car-companies.htmlhttps://www.wsws.org/en/articles/2020/09/08/gmhm-s08.html