Sundar is neither a founder nor has been a practicing Engineer. That's gotta hurt a company like Google which is mostly Engineering driven. I guess Google at this point just keep churning through systems because Engineers are incentivized to show impact and rarely end up creating new good products. Adding tons of new engineers is also probably hurting their overall quality and velocity.
Back in around circa 2006, Microsoft one day suddenly decided to remove Google search and replace it with Bing on their default browser, IE (which was still number one back then). This threatened Google's revenues to a considerable extent as online search is one of the major source of their income.
At that time, it was Sundar Pichai who was in the forefront of managing some quick OEM contracts with Dell, HP, etc., so that Google toolbar was installed by default on all their computers. Google toolbar ensured that users were shown a confirmation dialog and were given the option to make Google search the default again! This later ensured Sundar's rise in power and respect that ultimately made him CEO one day.
One can of course argue that Google is such a superior engine compared to Bing that the users would have visited google.com anyway (which will also result in that option to make it default). However, its also true that most users will not take the pain of changing their setup if it already works! So who knows, if Sundar's intervention hadn't happened at that time, maybe Bing and Google would be on an equal footing today!
EDIT
Source: Straight from the horse's mouth (Jeff Nelson, Chromebook inventor and former Google employee): https://www.quora.com/What-did-Sundar-Pichai-do-that-his-pee...