One big question that plagues the minds of many non-muslims, “why are there different muslims?” It seems so weird. The truth is there only is one type of muslim.
A muslim; the one who submits themselves to the will of Allah.
But this is the sad reality, not all muslims are on the same page. Some hope for the pleasure of Allah, and Jannah. Some hope merely to be saved from the fire. Some hope for the largest mansion, others the most expensive car, others the biggest bank account and fewer still want a football team of kids…And this is where the problem lies. We have forgotten our true purpose, and have attached ourselves to aspects of the worldly life, forgetting that it is a temporary abode which will inevitably come to an end.
Back to the question. Islam is a complete way of life that governs the way a person lives, from the moment one wakes up until he returns to his bed. In this sense one may describe islam as a package, you either take the whole package or leave it, it cannot be tailored to suit one’s preferences. One of the causes for different muslims, is that many have adopted Islam and turned it into a buffet! They pick and choose what they want and layer it on their plate, leaving things that don’t fit their lifestyle. So in other words they build Islam around their established lifestyle, rather than basing their lifestyle on Islam, which is how it should be. Many attempt to bargain with Allah, and some go ‘fatwa shopping’ picking the most lenient of answers to their daily problems in order to have the easy way out. It is these people who crown the ignorant as ‘Great Shaykh’ and ‘Maulana’ and ‘Mufti,’ in attempt for the ignorant to give them a carte blanche to do as they please.
But little are they aware that Allah says, “O you who have believed, enter into Islam completely [and perfectly] and do not follow the footsteps of Satan. Indeed, he is to you a clear enemy.” (Surah Baqarah 02:208) to pick and choose from the religion is a trap of Shaytan.
Another reason why there are different muslims is ability. Islam is a religion that was chosen for us by Allah, our Creator who knows us best. When he chose for us Islam, He knew that each person is an individual having different characteristics and abilities. While the core of islam is fixed is obligatory upon every muslim, there are voluntary matters that are flexible. For example there are the obligatory prayers; which are compulsory upon every muslim, but there are in addition to that voluntary prayers which one may choose to do, if they have the ability. Thus some have the ability to ‘do more’ and others stick to the bare minimum, which is perfectly fine.
Another aspect which causes differences is means. For example, one should stand to pray, but if one is disabled, he lacks the means to do so, Islam permits that he sits, and if he unable to sit, Islam permits him to lay down. Similarly one who does not have the means to give charity is absolved from this responsibility. Again, Allah knows each one of us, and He knows the means available to us, as long we use the means and do not neglect them and strive hard all is ok.
The fact that faith (iman) fluctuates, is also a reason of difference. One may feel spiritually strong one day, but the next day he feels weaker, and in fact faith can fluctuate within the same day. Moreover each individual is on a different level of faith based on their ability, and devotedness. It is the choice of individuals to work towards increasing the faith.
I hope this brief few words have summarised the main reason for differences amongst muslims. The topic of sects, groups and partisans (known as hizbiyyah) is a whole other issue which has no end, and one that needs a lot more attention detail. Thus I have explained the main reasons for differences amongst the main body of muslims. These points mentioned here will explain why one woman dons hijab and another walks exposed, why one shaves his beard and another leaves it to grow. I hope you get the picture, and this is in no way a scholarly piece of work.