There are many factors. We had an autocratic government headed by Maumoon Abdul Gayyoom for 30 years. He is an Islamic scholar who studied at Al Azhar University in Egypt. He presented himself the the supreme authority on Islam in the country and promoted a form of conservative Islam which was used as a tool of political control. However hardline Wahhabi extremists (usually with Saudi or Pakistani education) who went beyond that level of conservatism were suppressed.
With the arrival of liberal multiparty system in the 2000s, the Wahhabis could run around freely. They established several organizations to spread their message and one of their political parties even took control of the Ministry of Islamic Affairs. Here, Islam is a mandatory subject in school from Grade 1-12, and all school textbooks on the subject of Islam are not much different from what you might find in Saudi Arabia.
These extremists also used the aftermath of 2004 Tsunami as an opportunity to spread propaganda about how it was Allah's punishment for not following the proper version of Islam. Particularly blaming it on women not wearing the hijab. Within a few years the hijab went from being worn by a minority of women to a majority.
And most importantly the socioeconomic conditions in our densely populated capital with its growing problem of unemployment, drug abuse, and criminal gangs provide many recruitment opportunities for the Wahhabis. Some of them are former gang members seeking redemption.