The pathfinder mission, although it only lasted about three months, far exceeded the goals set forth for the mission. It had far reaching affects on our understanding of the planet and, especially, the technology that was used. Our grasp on the possibility of water was tightening and all the pieces were falling into place.
Odyssey and Express were next in line to extract what they could from Mars and that definitely did that. They used spectrometers to measure hydrogen levels and when they found areas where the readings began to go off the charts, they knew that was happening only in the presence of large amounts of water ice, and very close to the surface.
As we know now, one success leads to another attempt, especially in the space industry. The Pathfinder, Odyssey and Express missions were very informative but NASA wanted to get closer, deeper into what was going on at surface level. The Mars Reconnaissance Orbiter (MRO), which was in essence a $720 million camera, was launched and began taking pictures of areas of landing interest all over the planet. Weather patterns were followed closely and meanwhile the scientist slowly were narrowing down areas for future landing sites. Also a new system of data transfer to and from Mars was being tested and as it turns out was a much quicker method of data transfer.
These landers, orbiters, probes and rovers were the front runners of Martin exploration and will always be held in high regard for their contributions to a greater understanding of a complex planet. As is a theme in most of my posts, there needs to be a sense of momentum building for the public to catch on and for the money to start flowing into these projects. Nothing does that better than a series of successes that are accompanied by great photos and irrefutable evidence of a watery/icy planet. NASA took this new found Curiosity and ran with it.