250k daily is really a huge amount even though bitcoin is used worldwide
No. 250k is very small (albeit *big* for something new like Bitcoin). In comparison, Visa does 2000 TPS on average which is over 150 Million transactions per day.
but I see now that the trending of making new transaction is huge and within a few seconds there are lots of transaction made (based on blockchain.info)
A lot of factors suggest that it was a spam attack (actually a preparatory one; the second wave will come soon).