I just can't seem to remember what caused this huge drop in the record lap time between 2005 and 2006. 2 strokes were phased out long before that. So what gives?

https://i.redd.it/bqgwzeo7ps211.jpg
Submitted June 08, 2018 at 04:26PM by capj23 https://www.reddit.com/r/motogp/comments/8pksgl/i_just_cant_seem_to_remember_what_caused_this/?utm_source=ifttt