was about to ask the same Q.

HLB got one of the best customer service for banking.

Ambank visa infinite come with buy 1 free 1 in lemon garden

Possibly to park FD funds.

Certain banks has special offers for FD from time to time.

Current normal FD rates of 2.1% is not satisfactory. So banks have offers up to 4% for a certain period in order to maintain high number of deposits. (for reference, ASM for non-bumis only offer 4-4.5%)

FD investors typically chase these offers because not all banks offer it permanently and the offers will not roll-over to next period. And also ASM is limited for these NONs.
For example AMBank currently has 3.6% for 10 months eFixedDeposit. So these people will open account, deposit money whenever Ambank has an offer and will switch their fund to other banks when their offers are better.

They don't need an ATM card or visit physically to transfer their funds. All can be done online.
Don't think these people doing this kind of FD chasing are playing with tens of thousands only, it could be hundreds of thousands of RM or even millions.