Ismael marked his 46th birthday in style as West Brom retained their unbeaten Sky Bet Championship record and took top spot from Bournemouth.
Karlan Grant, Alex Mowatt and Matt Phillips were all on target, while Cardiff defender Curtis Nelson added to the home side's misery by putting through his own net.
"I want to give a massive thank you to the players for the performance and the three points," Ismael said.
"When you make sacrifices to your family, it is performances liken that that make it feel worth it. It was a great evening for us.
"We are now moving more towards my vision for this team. I want us to stay confident and move further in the right direction.
"But we have to stay forceful. We have another difficult game on Friday night (away to Stoke) and we need to make sure we do the same as we have done here."
Grant struck his third goal in two games inside five minutes to put Albion on the road to victory.
Albion turned their first-half supremacy into goals after the break as Nelson sliced into his own net before Mowatt's vicious half-volley and substitute Phillips' late strike completed the rout.
"When we scored in the first half we set the tone," Ismael said. "But I told them they needed to stay on the front foot.
"We knew Cardiff would come at us strongly at the start of the second half, but we scored the second at the right time and that gave us the confidence to go and score more.
"All the goals were brilliant and showed the confidence and mentality of this team."
Cardiff manager Mick McCarthy had to endure chants of 'You're getting sacked in the morning' from both sets of supporters following a sixth defeat in seven games.
McCarthy, who has seen his side concede nine goals in two games, said: "People singing that at me... the away fans, that doesn't bother me one bit.
"When the home fans start doing it, that's a different ball game all together.
"I fully understand the fans and I have no complaints about them at all. I share their frustrations and I can't say we don't deserve it.
"We need a result and fast to get some momentum back quickly. I'm not taking any comfort in anything at the moment.
"I want to turn it around and make sure we do better. We will carry on and working as hard as we can to do that."