I don't know what is the benefit of making the idols?
Before I answer, let me point out that it seems that Muslims often equate the use of icons, statues and other physical objects in religious services with idolatry, which would be mistaking such objects ("idols") with supernaturally significant powers.
Idolatry happens. If nowhere else, it certainly happens in cargo cults. And while I don't personally find that as much of a worry as monotheism itself, I don't disagree that idolatry happens in more mainstream religions as well.
Idolatry is not all that easy to define - a lot of it is in the eye of the beholder - but we can probably agree that it happens to some degree. There are definitely people who attribute some measure of supernatural significance to various statues and sacred relics around the world, even to abstract geometrical forms.
Still, how significant is that, and why? It shows that people don't always agree on what is religiously significant, certainly. It hints that at least some people are mistaken about their objects of worship, even if there is no consensus on who exactly those people are.
I assume that from the perspective of a reasonably typical Muslim, one who sincerely believes that it is very important not to be mistaken about who the only true God is and, specifically, who finds it very unadvisable to worship anything other than that God, it can be a big deal to potentially "worship a false God".
But what is it that makes a God false, exactly?
Perhaps surprisingly, a large part of it is in the worshipper himself or herself.
I am not a believer in revealed religions myself, but it seems clear to me that even if there is such a thing as a true revelation on scripture from the one true God, it is definitely possible to mishandle such revelation in such a way as to develop a seriously misguided idea of who or what that God would be and what proper worship of Him would be. That leads to a very dangerous and in my opinion very common situation, where various people hold conceptions of the divine that are mutually incompatible yet fail to fully acknowledge that, and in fact go out of their way to avoid acknowledging those disagreements.
Perhaps there is some form of hope that as time goes by they will meditate on the revelation and reach more of a common ground. Perhaps there is some other reason to avoid pointing out flat out that their views are mutually exclusive. Either way, it happens. It happens very often indeed.
And it is not a problem if we learn to accept it and deal with it respecfully and reasonably. People won't always agree on many things big and small even when they are utterly sincere and well meaning. There is no reason to expect them to consistently agree about such a personal thing as God.
We atheists know that and accept that fairly easily, because we have little reason to avoid realizing how varied are the conceptions and expectations regard God.
Hindus, I would think, also know and accept that God is ultimately a very personal belief, that can and will vary considerably from one person to the next. They also largely learned to deal with that in a positive, constructive way: they acknowledge a wide variety of beliefs about the nature and identity of the divine and even establish distinct schools of thought according to specific beliefs. But they perceive no particular need to establish who is "right" and who is "wrong" on that regard, quite possibly because they realize at some level that there is no universal correct answer. It does in fact, and legitimaly, depend to a significant degree on the personal inclinations of the devotee.
Why so? Mainly, I think, because the relationship between devotee and Deva in Hinduism is far more respectful of individual people and their varied needs, abilities and vocations than it is usual for Muslims to understand and easily accept. It probably helps to be well aware and accepting that disagreements about God will happen, but do not have to spell doom. Hindus have been disagreeing among themselves on the nature, number, and even origin of Devas for literal millennia. That does not seem to have much more consequence beyond leadng to the creation of different schools of thought where people teach with their own answers for those questions. There is no need to insist that others must reach a consensus on those matters.
I guess I could feel differently if I feared that eternal hellfire could be my destiny after my death unless I learned to worship the One True God before then. But I don't, and I doubt I ever will.