Eventually Astro replied one of the Facebook user regarding the reason of the channel cessation below:
Astro continuously reviews its content proposition to offer the best choices and a variety of compelling content for our customers. In line with this, any channel that is unable to fulfil these objectives will be discontinued. To this end, we regret to inform that effective from May 16, 2016 at 00:01 hours, Astro HITZ (Ch 705) will cease transmission on the Astro platform. We apologise for any inconvenience caused
It is believed that the reason behind the cessation of Astro Hitz is due to very low viewership rating.
Alternatively, Channel [V] HD is available on TM Hypp TV platform, (Hypp TV channel 604).