Wanderers boss Ainsworth introduced the 19-year-old at half-time and he went on to score his first career goals to leave Pools winless this season after six games in Sky Bet League Two.
After a first-half which was dominated by the hosts, without finding a way through, Kretzschmar turned the game in Wycombe's favour.
His 47th-minute corner was headed inches wide by Steven Craig before he found the back of the net in style.
Picking up possession, he turned to goal and cracked in a low shot from 25 yards and then deftly chipped the ball over goalkeeper Scott Flinders after a quick counter-attack.
"Max won it for us and what a whirlwind start to his career,'' said Ainsworth. "He gave us more energy, is a goal threat and I'm so pleased for him. He's all smiles and is a top, top lad.
"He came back in the summer after doing everything I've asked of him. He worked really hard to come back and every word I say he takes it in. He does things 100 per cent and gets the rewards.
"What a day and the lads are buzzing for him. He put two good finishes away, he's got that about him and he has composure - a very technical player. It's the physical, energetic side, the winning headers side, the competing-against-men side of the game to come and now he has that.
"He is now a big part of the side and I couldn't be happier - a good guy who deserves every bit of praise.''
Ainsworth added: "It's really pleasing, the second-half performance was good but our first-half show wasn't good enough by a mile.
"We said at half-time we had to improve but I didn't lose my rag at the break, I was more constructive.''
Substitute James Poole headed in from close range in injury time to score Hartlepool's first league goal of the season but it was too little, too late for the hosts.
New Pools' boss Colin Cooper, whose side beat Bradford 5-0 in the Johnstone's Paint Trophy in midweek, was frustrated.
"The first goal was vital. It proves the case with us,'' he said.
"The instruction was to start the second half at a high-tempo and put Wycombe on the back foot and it didn't happen
"The two goals they scored weren't good goals, but enough to give them the points.
"The whole place felt flat - the players, the crowd. There was a slow tempo with the referee, even though I asked for it to be speeded up throughout. It gets frustrating.
"I felt the officials were allowing Wycombe to slow the game down and not allow us to get into any tempo.
"The start to the second half wasn't in any way, shape or form what I expect.''
"Loads of huffs and puffs and knock-downs and it didn't fall for us like it did the other night. We look at reasons why.``