Timeline - 1985 to 2007 - what happened?

[hawkangel]

I have rediscovered Transformers again in my 40s and have been collecting and watching for a little while now.
One thing I’ve always wondered with the Transformers G1 series and Movie.
The movie is set in 2005 (some places say 2007). The first two season of the Tv series is set in 1985.
My question is : What happened between these years? That’s more than 20 years of an unaccounted time.
I haven’t watched other shows like Beast Wars (which I assume is set in the far future), but I have read a bit of the Marvel Uk comics which has a bit of Time Travel involved between 2005 and 1985.
From what I gather, Seasons 3 and 4 of the original series are set in 2007.
(Please don’t answer “It’s just a Tv show!”)