Here is a chart from prenoms.com that shows the popularity of Maeva the last 80s years. If you scroll over the green parts on the chart, the usage of Maeva seems to begin in 1970. It says 9 girls were born in France with the name Maeva. It seems to have gone up subsequently since and in 1988, it really skyrocketd.
According to tous-les-prenoms.com Maeva first came into wide usage in 1975. It doesn't really give us a reason why it suddenly became popular in France, just that the meaning of "welcome" was appealing to parents, and that it corresponds with a more traditional, yet old fashioned French name, Bienvenue, which has the same meaning as Maeva.