First of all the problem is between the followers of Islam on one side and all other communities on other side. If you anaylise, you will find that in the most of the countries wherever muslims are residing they are creating trouble.
No other communities have such strong feelings against each other.
This all has been happening since long. Bharat being a follower of Sanatan Philosophy is a believer of “Vasudev Kutumbhkam” policy and that’s why Bharat is having the maximum number of religions, languages, culture. We have welcomed and adopted every outcomer under our tradition “Atithiti Devo Bhav” but if you see the history Bharat has paid a very heavy cost for this tradition. The akhand Bharat which you might have heard nowadays also was starting from todays Iran and included Burma, Bhutan, Nepal, Tibbet. Bangladesh, Afganistan, Pakistan. Due to our policies, we being clean hearted and polite welcomed all and in that invaders also found easy access. Such invaders which were followers of Islam mostly looted Bharat and forcibly tried to capture the whole country. They forcibly converted Hindus into muslims, killed lakhs of people who had not obeyed to their orders, molestated and raped women, kidnapped them and sold them in Afganistan. This animity has roots to that time.
If you see even the Britishers came to Bharat and ruled but we dn’t have issues with them now. They also looted but they had not done sins as done by Muslims.
Muslims even after taking a whole country for themselves are still demanding and even after they ruled for 800 years and 70 years of appeasement are still illiterate and poor because their priests teach them hatred. Their small children are taught to hate and establish the rule of Islam. They dn’t believe in living cordially rather they just want to setup their rule.
Now regarding your main point that why it is so? Let me tell you that in past their was no use of social media as of today and hence the communication was less. Now the truth of such people is coming out and is spreading everywhere, so the resentment against their wrongdoings is also visible.
If you see there is no hatred amongst Hindu, Bodh, Sikh, Jain, Parsi, Christian. It is only where muslims are creating trouble. The recent Delhi and Bangalore riots are example of it. Hope you understand.