yes, it is disorientating getting out of the aircraft and you would normally inflate your lifejacket once clear. I don't know if he did that or not but it would have made getting back into the helo nigh on impossible.
If he did go back in (do we know that for sure) 3 times (why when there were only 2 others in it) but with the floats inflated and the helo inverted and stable then yes, it is an admirable thing to do and I suspect in those conditions, properly suited up and with adrenaline pumping, most of us would have done the same to rescue friends.
Sure Q would, like you, see it as a natural duty to go back despite the strident professional advice in HUET training to "never go back in". From the interview seems heli was on its side and sinking fast. First time back in to activate float switch (which remarkably worked considering electric release submerged) second time for David, third time for Charlie. 1m visibility, low light, cold water, wreckage adding to the task. Also activation of floats caused heli to invert from its side extremely quickly (inflation time is 1s to 2s in the book) no doubt adding to the challenge.