If the end goal is a preferrable stealth, certain and total Islamization of a theoretical Country X, the symptom must necessarily be a jostle for dominance amongst its potential overlords.

Imagine a scenario if you will in theoretical Country X where the Saudi Arabian backed Sunni gets into a showdown with the Iranian backed Shiite. Both being the two sides of a pseudo religious hyper ideological divide of a similar entity - Islam

Suppose if you will, that theoretical Country X is predominantly Sunni. Then you will be playing Ostrich if you suppose even for a second that the Sunni led Government will fail to employ the instrument of state as a battering ram against its recalcitrant twin.
The Sunni will ultimately quickly and surely overrun the Shiite in a bloody massacre as is customary with Islamists. It must declare all Shiite affiliates as terror related by means of justification.

All civil and secret services, police force, security outfits, the armed forces, judiciary, legislature and even the fourth estate I.e. media must be co-opted in the attritive destruction of the Shiite infidels. Why are you acting surprised, does the Leopard change its spots?

So what's a smart Shiite supposed to do?

1. Convince the predominantly Southern Christians in the theoretical Country X that the Sunnis have a diabolical Islamization agenda; the objective being to sow mistrust, discord and enmity in the populace.

2. Convince disgruntled elements in the populace that all such interests are eligible for convergence.

3. Open the borders, let the Shiite mujaheeds pour into the country like rats waiting for the call to jannah as you bid them hold their horses for the appointed time; bring in logistics and amunitions in millet bushels and on the backs of donkeys if necessary.

4. Make sure to get the official backing of all Shiite Countries; they support you with cash and ammunition and reassure you of protection once things get intolerable.

5. Infiltrate all arms of governance. This goes without saying, it is to your interest that the government implodes on itself while you rush in and take the spoils.

Ultimately the Shiite are vastly out matched, they have to be more proactive than the Sunni in the theoretical Country X.

This stated; for the sleeping Southies/Christians who predominate in the southern part of this theoretical Country X and who have succeeded in falsely convincing themselves that the scenario above is an Islamic problem, think again fool!

Don't believe for one second you will be spared if this scenario plays out; you are the pawns in this cosmic chess match, your submission will be swift and bloody as all such Islamic revolutions are. The symptoms are already clear enough for the blind to see and loud enough for the deaf to ear....a wise cripple takes caution for a declared war.

Enjoy yaself