My 2 cents.
1. US behind this.
I think ultimately the US is behind this.
- The US and its CIA in conjunction with its local sub-contractors such as the ISI in Pakistan, the MIT in Turkey and the Saudis is known for being the ultimate creator, sponsor and beneficiary of Salafist-Jihadist terrorists. The CIA role in sponsoring Islamic militants in Afghanistan against the Soviets is not even denied.
- Prior to any real terrorism in Bangladesh or anything of the ISIS nature (ISIS is a CIA-created group) Bangladesh was perceived as stable, then one day bizarrely and mysteriously the Australians refused to send their cricket team to Bangladesh citing "security" reasons. Then shortly after an Italian national was killed in Bangladesh, almost as if to vindicate the Australians.
The murdered Italian national was the first person in this new wave of Islamist violence to be killed.
The Australians would only have behaved in such a way if (mis)informed/ordered/encouraged to by the Americans. Not the actual Australian cricketing authorities but the Australian "intelligence"/"security" establishment which told them not to go to Dhaka.
2. The perpetrators were Bangladeshis.
The culprits were from middle class Dhaka families and in middle class circles across the Muslim world being "religious" can be frowned upon, it's seen as "uncool" and even somewhat of a stigma.
Despite this they became radicalized. The questions are who, how, where? Who radicalized them, how and where? Then a solution needs to be found.
3. US support for Islamists in Bangladesh
Instead of sympathizing with the relatively "secular" (in a Bangladeshi context) Awami League and condemning the political Islamists that these militants are an off shoot off, the American media is actually doing the reverse and saying the Bangladeshi opposition (many whom are Islamists) needs to be treated softer.
The US supports Jamaat e Islami in Bangladeshi, partly to act as leverage against Hindu India and to promote divide and rule in the region thus perpetuating western hegemony.
Notice how no western media article will say anything negative about Jamaat e Islami or have lines such as:
"With the latest atrocity in Dhaka, all eyes are now being cast on political Islamists in particularly Jamaat e Islami, the controversial anti-independence organisation. Many in Bangladesh are calling for action against militant Islamists".
NO.
If anything the American media spin is that this atrocity is Hasina's fault because she has been victimizing Islamists i.e. HASINA = BAD, ISLAMISTS = GOOD.
4. India and this attack.
India and Russia are fully aware of the US' malicious agenda in the bay of Bengal which includes fermenting division between these "brown darkies" be they Hindu or Muslim, trying to gain a US military presence in Bangladesh in the form of "teams of US military advisors" or "US security teams" sent to "help" Bangladesh.
Once these security teams are sent, they have to be hosted, thus their residence becomes a de facto US military base. As a giant nuclear power there will then be security protocols between Bangladesh and these "advisors" and due to being US passport holders and security officials they are "untouchable".
This US influence then supplants the relatively good relations between Bangladeshi and Indian security teams.
I wouldn't go as far as to say the US wants to create a new Syria in Bangladesh and create a Hindu-Muslim conflagration, and nor can it for various reasons e.g. India is more capable of preventing conflict than the Baathist regime in Syria, however the US definitely wants to cause tension.
For now the most immediate action which the GOB (Government of Bangladesh) must take apart from all the necessary security investigations, forensics is to ask this man below to make a special 1 hour du'a (supplication) at Eid for an end to terrorism in Bangladesh, peace in Bangladesh and peace between "members of all religions" (code for peace between Hindu and Muslim i.e. India and Bangladesh, i.e. to prevent the US goal of causing conflict between India and Bangladesh).
Fariduddin Masud, leader of the biggest Eidgah gathering in Bangladesh and anti-terrorist, anti-Jamaati Islamic scholar.