Not to mention it led to her downfall. Threatened her coalition, the vote of no confidence, Azgeda threatening to split away. Clarke made her look weak doing what she couldn't. If Titius had not accidentally offed her I think her demise was inevitable. Making a deal with the grounders biggest and greatest threat when everything was going according to plan was a blunder for sure. Lexa knew what Mt. W were up to, had they succeeded they would have been able to freely move about without the need for suits or oxygen tanks and they had superior weapons and would have been looking for ground to settle in grounder held territory.