I think Gatekeeper was just somewhat of a fluke or a long pause for coasters after Maverick. If you look back at Cedar Point's history, since the 80's they've built new/record breaking coasters every few years. Magnum, Mean Streak, Rapor, Mantis, Millennium Force, Wicked Twister, and Top Thrill Dragster (plus a kiddie coaster in there) were all built in a timeframe of four years max in between (Mantis and Millennium Force).
After Maverick, and acquiring the Paramount parks, they wanted to focus on other parks, and reimagine the image of Cedar Point being more well rounded (not that it wasn't already). So, they took a five year break (2008-12) at Cedar Point, then got right back on track with Gatekeeper.
Two years of pretty minor investments relative to the parks history (excluding the Breakers renovation which was funded from a waterpark sale) and you have another great opportunity to reimagine the Marina gate for what is presumably much more affordable than Gatekeeper.
Anyways, that just my theory. It's not that this was particularly sped up, it's just the period of time between Maverick and Gatekeeper was a sign of change for the company.
Or the entire US economy tanked (upper midwest especially hard) and Cedar Fair didn't feel the need to spend on a park that had a ton of coasters already.